Succeed in getting me to hold a horse (6)
I believe the answer is:
manage
'succeed in' is the definition.
'me to hold a horse' is the wordplay.
'to hold' is an insertion indicator.
'horse' becomes 'nag' (nag is a kind of horse).
'a'+'nag'='anag'
'me' placed around 'anag' is 'MANAGE'.
'getting' acts as a link.
(Other definitions for manage that I've seen before include "Control, direct, run" , "Be in overall control of" , "Run, administer" , "Exercise control - don't fail" , "Handle, cope with" .)