Dealt with a poor horse during medical (7)
I believe the answer is:
managed
'dealt' is the definition.
('manage' can be a synonym of 'deal')
'a poor horse during medical' is the wordplay.
'poor horse' becomes 'nag' (I've seen this before).
'during' indicates putting letters inside.
'medical' becomes 'med' (common abbreviation).
'a'+'nag'='anag'
'anag' put into 'med' is 'MANAGED'.
'with' is the link.
(Other definitions for managed that I've seen before include "Coped" , "Controlled, was in charge of" , "Supervised (staff)" , "Contrived" , "Ran, administered" .)