  We present [CII] synthetic observations of smoothed particle hydrodynamics
(SPH) simulations of a dwarf galaxy merger. The merging process varies the
star-formation rate by more than three orders of magnitude. Several star
clusters are formed, the feedback of which disperses and unbinds the dense gas
through expanding HII regions and supernova (SN) explosions. For galaxies with
properties similar to the modelled ones, we find that the [CII] emission
remains optically thin throughout the merging process. We identify the Warm
Neutral Medium ($3<\log T_{\rm gas}<4$ with $\chi_{\rm HI}>2\chi_{\rm H2}$) to
be the primary source of [CII] emission ($\sim58\%$ contribution), although at
stages when the HII regions are young and dense (during star cluster formation
or SNe in the form of ionized bubbles) they can contribute $\gtrsim50\%$ to the
total [CII] emission. We find that the [CII]/FIR ratio decreases due to thermal
saturation of the [CII] emission caused by strong FUV radiation fields emitted
by the massive star clusters, leading to a [CII]-deficit medium. We investigate
the [CII]-SFR relation and find an approximately linear correlation which
agrees well with observations, particularly those from the Dwarf Galaxy Survey.
Our simulation reproduces the observed trends of [CII]/FIR versus $\Sigma_{\rm
SFR}$ and $\Sigma_{\rm FIR}$, and it agrees well with the Kennicutt relation of
SFR-FIR luminosity. We propose that local peaks of [CII] in resolved
observations may provide evidence for ongoing massive cluster formation.

Astrophysics of Galaxies