Unfashionable group making a start (6)
I believe the answer is:
outset
'a start' is the definition.
('outset' can be a synonym of 'start')
'unfashionable group' is the wordplay.
'unfashionable' becomes 'out' ('out' can be a synonym of 'unfashionable').
'group' becomes 'set' (set is a kind of group**).
'out'+'set'='OUTSET'
'making' acts as a link.
(Other definitions for outset that I've seen before include "Inception" , "Kickoff time?" , "launch" , "Opening stage" , "origin" .)