Military academy using smooth wood (9)
I believe the answer is:
sandhurst
'military academy' is the definition.
(I've seen this before)
'smooth wood' is the wordplay.
'smooth' becomes 'sand' (sanding is a kind of smoothing).
'wood' becomes 'hurst' (I've seen this before).
'sand'+'hurst'='SANDHURST'
'using' acts as a link.
(Other definitions for sandhurst that I've seen before include "Village in Berkshire - military academy" , "Military college at Camberley, Surrey" , "Seat of the Royal Military Academy" , "Training college" .)