Victor stuck in single crack (5)
I believe the answer is:
solve
'crack' is the definition.
(I've seen this before)
'victor stuck in single' is the wordplay.
'victor' becomes 'V' (phonetic alphabet: alpha, bravo, charlie etc.).
'stuck in' means one lot of letters goes inside another.
'single' becomes 'sole' (synonyms).
'v' going inside 'sole' is 'SOLVE'.
(Other definitions for solve that I've seen before include "Find the answer to this clue, for instance" , "Work out (a problem)" , "Work out (a clue)" , "Find the answer to a puzzle" , "Unravel (a problem)" .)