Mistress maybe rather like a team member (1,3,2,3,4)
I believe the answer is:
a bit on the side
'mistress' is the definition.
(I've seen this before)
'rather like a team member' is the wordplay.
I cannot really understand how this works, but
'rather' could be 'abit' ('a bit' can mean rather or to some extent) and 'abit' is located in the answer.
'team' could be 'side' (both can mean a sports team) and 'side' is found within the answer.
This explanation may well be incorrect...
'maybe' is the link.
Can you help me to learn more?
(Other definitions for a bit on the side that I've seen before include "secret of a cheat?" , "that endangers union arrangements?" , "Some information about team" , "as sauce on a plate?" , "illicit lover" .)