Manage to exercise (3)
I believe the answer is:
run
I believe this clue is a double definition.
'manage' is the first definition.
(I've seen this before)
'exercise' is the second definition.
'to' is the link.
(Other definitions for run that I've seen before include "A single" , "Administer" , "Tear in a stocking - hurry" , "Manage (eg, a company)" , "goal for England player?" .)