Keen shooter close to landing shot in the centre (4,2)
I believe the answer is:
gung ho
'keen' is the definition.
(I've seen this before)
'shooter close to landing shot in the centre' is the wordplay.
'shooter' becomes 'gun' (I've seen this in another clue).
'close to' says to take the final letters (the 'close' to the word).
'in the centre' says to take the centre.
The middle letters of 'shot' are 'ho'.
The final letter of 'landing' is 'g'.
'gun'+'g'+'ho'='GUNG-HO'
(Other definitions for gung ho that I've seen before include "Overly zealous" , "Eager, zealous" , "Enthusiatic about war" , "Very (sometimes over-)enthusiastic and dedicated" , "Full-on, maybe jingoistic" .)