Tower needing airmen to be trained on time (7)
I believe the answer is:
minaret
'tower' is the definition.
(minaret is a kind of tower)
'airmen to be trained on time' is the wordplay.
'to be trained' indicates anagramming the letters (to train can mean to grow something into a shape).
'on' means one lot of letters go next to another.
'time' becomes 't' (**).
'airmen' anagrammed gives 'minare'.
'minare'+'t'='MINARET'
'needing' is the link.
(Other definitions for minaret that I've seen before include "Mosque turret" , "Slender tower with balconies" , "Slim tower of a mosque" , "tower in the Middle East" , "Mosque's tower" .)