Firm has obligation to entertain top lady in camp (7)
I believe the answer is:
coterie
'camp' is the definition.
('coterie' can be a synonym of 'camp')
'firm has obligation to entertain top lady' is the wordplay.
'firm' becomes 'co' (a firm is a company).
'has' says to put letters next to each other.
'obligation' becomes 'tie' (I've seen this before).
'to entertain' is an insertion indicator.
'top lady' becomes 'er' (I've seen this in other clues).
'tie' going around 'er' is 'terie'.
'co'+'terie'='COTERIE'
'in' is the link.
(Other definitions for coterie that I've seen before include "Set" , "Exclusive group with shared interests" , "Small exclusive group of friends" , "Exclusive circle of people with common purpose" , "Exclusive social circle" .)