A cosmetic crack (3-5)
I believe the answer is:
one-liner
'crack' is the definition.
(I've seen this before)
'a cosmetic' is the wordplay.
'a' becomes 'one'.
'cosmetic' becomes 'liner' (I've seen this before).
'one'+'liner'='ONE-LINER'
(Other definitions for one-liner that I've seen before include "Witty remark contained in a single sentence" , "Quick joke?" , "Single sentence jokes" , "Quick gag" , "Short joke - witty remark" .)