Rob worked around first restaurant (6)
I believe the answer is:
Here is my best explanation:
'restaurant' is the definition.
(bistro is a kind of restaurant)
'rob worked around first' is the subsidiary indication.
'worked' indicates an anagram.
'around' indicates putting letters inside.
'first' becomes 'ist' (**).
'rob' is an anagram of 'bro'.
'bro' placed around 'ist' is 'bistro'.
(Other definitions for bistro that I've seen before include "Cafe/restaurant", "Cheap restaurant", "Modest restaurant", "Restaurant", "Little restaurant", "Small French bar and restaurant", "Informal French restaurant", "Small restaurant - robs it (anag)", "Small bar-cum-restaurant" and "Small informal French restaurant".)