Mum having setback in Friends? (5)
I believe the answer is:
mates
'friends?' is the definition.
(mate is a kind of friend)
'mum having setback' is the wordplay.
'mum' becomes 'ma' (ma can mean mother).
'having' is a charade indicator (letters next to each other).
'setback' becomes 'tes' (I've seen this in other clues).
'ma'+'tes'='MATES'
'in' acts as a link.
(Other definitions for mates that I've seen before include "Pals, pairs" , "Friends among the ship's officers" , "Pals or spouses" , "Husbands, wives or pals" , "Partners or pals" .)