What is this anime about people who can transform themselves into giant robots with the help of a device/talisman? I only saw the last part of this Anime. A few minutes. So, I cannot give many details.
I think it was a movie and I think it was around the 2nd half of the 1990s. Because it was on a weekend program where they showed Anime movies and once "X (1999)" was one of them. 

What I remember from that short scene:


The Anime is about people, who can transform themselves into giant robots with the help of a device/talisman (?). However, the transformation rips their clothes apart and when hey change back, they are totally naked.
The protagonist is a girl. She has straight, shoulder-lenght, brown(ish) hair and she wears it in pigtails maybe. Anyway, her hair is tied up somehow. Either she cannot transform till the end of the movie or she has problems with fighting... but in the end she transforms and fights well.
There is and older guy (not old!), who may be her "teacher", who teaches her how to transform(?) He has brown hair and glasses I guess. In that end scene he came to help the girl out but she did well on her own, so he just watches and changes back. Being experienced, he brought spare clothes with him, but there is a giant dog (I think it is his) that takes them. So the guy ends up chasing the dog naked. They were under a bridge that time.
The art was great and detailed.


This is ALL I remember.
The series that OP was looking for is Moldiver, a 6-episode 1993 OVA anime series.



The female protagonist is Mirai, the brown-haired girl in the middle. And the glasses guy on the lower right corner is Hiroshi, her brother and inventor of the Mol Unit - the transformation device.

Plot summary by ANN:


  Hiroshi Ozora invents the Mol Unit, a device that makes its user invincible. His plans of becoming a super hero are short lived however when his sister, Mirai, accidently modifies the suit configuration. Now she is forced to save Tokyo by herself from the evil Machinegal and his gang of all-female androids.


Below is the screenshot 18 minutes into episode 2 showing Mirai getting her clothes ripped off when transforming with her clothes still on.



Below is a series of screenshot of Hiroshi getting naked inside the tunnel of the stadium to prepare for the transformation but failed (17 minutes into episode 2), after which he contacted Mirai and asked her to transform (above). When he was instructing Mirai (21 minutes into episode 2), a dog came and took his clothes away behind him.



There wasn't any scene of him chasing the dog, though.



When I first tried to identify the anime in question, I checked through the list of anime and manga in Clothing Damage trope, and Moldiver's screenshot kind of matches the description for the female protagonist.