Steal from fashionable man (5)
I believe the answer is:
Here is my best explanation:
'man' is the definition.
'steal from fashionable' is the subsidiary indication.
'steal from' becomes 'rob' (I've seen this before).
'fashionable' becomes 'in' ('in' can be similar in meaning to 'fashionable').
(Other definitions for robin that I've seen before include "Red and brown songbird", "Christmas songbird", "Small brown thrush", "Batman's assistant", "Name", "Small brown and red bird", "Bird on many cards", "Famous outlaw", "Batman's companion" and "Red-breasted Christmas card bird".)