Officer wants change in U-boat direction (9)
I believe the answer is:
subaltern
'officer' is the definition.
(subaltern is a kind of officer)
'change in u-boat direction' is the wordplay.
'change' becomes 'alter' (altering is a kind of changing).
'in' indicates putting letters inside.
'u-boat' becomes 'sub' (German submarine).
'direction' becomes 'N' (compass direction north).
'sub'+'n'='subn'
'alter' put within 'subn' is 'SUBALTERN'.
'wants' is the link.
(Other definitions for subaltern that I've seen before include "Army officer below the rank of captain" , "Junior officer" , "Lesser official" .)