Skipper in international leading reserves in (7)
I believe the answer is:
captain
'skipper' is the definition.
('captain' can be a synonym of 'skipper')
'international leading reserves in' is the wordplay.
'international' becomes 'cap'.
'leading' means one lot of letters go next to another.
'reserves' becomes 'ta' (I've seen this in other clues).
'cap'+'ta'+'in'='CAPTAIN'
'in' acts as a link.
(Other definitions for captain that I've seen before include "Naval rank" , "eg Hornblower" , "Leader" , "US policeman" , "Ship's commander" .)