Hard negotiation tactic succeeded in doing rather badly (5,7)
I believe the answer is:
horse trading
'hard negotiation tactic' is the definition.
(horse trading can mean hard bargaining)
'succeeded in doing rather badly' is the wordplay.
'succeeded' becomes 's' (genealogical abbreviation).
'in' is an insertion indicator.
'badly' indicates an anagram (letters in the wrong order).
'doing'+'rather'='doingrather'
'doingrather' is an anagram of 'horetrading'.
's' placed within 'horetrading' is 'HORSE-TRADING'.
(Other definitions for horse trading that I've seen before include "Hard bargaining (at yearling sales?)" , "Hard and shrewd bargaining" , "part of stable business?" , "Ordering hats (anag) -- ordering quadrupeds?" .)