Leave out exercise runs for captain (7)
I believe the answer is:
skipper
'captain' is the definition.
('skipper' can be a synonym of 'captain')
'leave out exercise runs' is the wordplay.
'leave out' becomes 'skip' (skipping is a kind of leaving out**).
'exercise' becomes 'pe' (Physical Education).
'runs' becomes 'r' (cricket abbreviation).
'skip'+'pe'+'r'='SKIPPER'
'for' is the link.
(Other definitions for skipper that I've seen before include "Head" , "being in charge?" , "Ship's captain (colloq.)" , "Senior pilot" , "who makes short hops" .)