Ruthless tactics in difficult social gathering (8)
I believe the answer is:
hardball
'ruthless tactics' is the definition.
(I've seen this in another clue)
'difficult social gathering' is the wordplay.
'difficult' becomes 'hard' (synonyms).
'social gathering' becomes 'ball' (ball is a kind of social gathering).
'hard'+'ball'='HARDBALL'
'in' is the link.
(Other definitions for hardball that I've seen before include "Tough tactics" , "A ruthless attitude in business or politics" .)