Number in team sarcastic (5)
I believe the answer is:
snide
'sarcastic' is the definition.
(I've seen this before)
'number in team' is the wordplay.
'number' becomes 'n' (n can represent any number).
'in' is an insertion indicator.
'team' becomes 'side' (both can mean a sports team).
'n' going within 'side' is 'SNIDE'.
(Other definitions for snide that I've seen before include "Delivering cuts" , "Dines (anag.)" , "Derogatory, showing malice" , "Derogatory, mocking" , "such remarks aren't nice" .)