Make a mistake to be wearing outrageous flares with transfers (9)
I believe the answer is:
referrals
'transfers' is the definition.
'make a mistake to be wearing outrageous flares' is the wordplay.
'make a mistake' becomes 'err' ('err' can be a synonym of 'make a mistake').
'to be wearing' indicates putting letters inside.
'outrageous' indicates an anagram (I've seen this in other clues).
'flares' is an anagram of 'refals'.
'err' placed inside 'refals' is 'REFERRALS'.
'with' is the link.
(Another definition for referrals that I've seen is " Directions or transfers to specialists, say, from rarer self".)