With advantage finally evaporating, finish becomes tense (10)
I believe the answer is:
pluperfect
'tense' is the definition.
(the pluperfect is a grammatical tense)
'with advantage finally evaporating finish' is the wordplay.
'with' means one lot of letters go next to another.
'advantage' becomes 'plus' (a plus is an advantage or benefit).
'finally evaporating' means to remove the last letter (the final letter evaporates).
'finish' becomes 'perfect' (perfect can mean to finish off and make perfect).
'plus' with its last letter removed is 'plu'.
'plu' next to 'perfect' is 'PLUPERFECT'.
'becomes' is the link.
(Other definitions for pluperfect that I've seen before include "Verbal tense" , "Tense with "had" and past participle" , "(In grammar) a tense - per cup left (anag)" .)