Pair beat poser to succeed (7)
I believe the answer is:
prosper
'succeed' is the definition.
(I've seen this in another clue)
'pair beat poser' is the wordplay.
'pair' becomes 'pr' (abbreviation).
'beat' is an anagram indicator.
'poser' is an anagram of 'osper'.
'pr'+'osper'='PROSPER'
'to' acts as a link.
(Other definitions for prosper that I've seen before include "Flourish, do well" , "Get rich" , "like Merimee, nominally" , "Succeed, flourish" , "Make good" .)