this clue, the word order seems wrong too. The English language doesn’t do “object” “subject” “verb” (as in “A [which] SPIRE secures”), especially when the verb is in the active voice. Looking at some other puzzles during the week, I noticed similar things. Is this a variant of English we might call “Setterlish”? On edit, Kevin's comments makes a good case that if "A" is a thing, "thing" SPIRE secures could give SPIR(thing)E. Far from obvious, I must say!
Times Cryptic No 27018