Working group needed for a start (5)
I believe the answer is:
onset
'a start' is the definition.
(onset is a kind of start)
'working group needed' is the wordplay.
'working' becomes 'on'.
'group' becomes 'set' (set is a kind of group).
'needed' says to put letters next to each other.
'on'+'set'='ONSET'
'for' acts as a link.
(Other definitions for onset that I've seen before include "Beginning; violent attack" , "Advent" , "Start - attack" , "Cast stone in attack" , "Start - opening moments" .)