Great squadron leader with skill (5)
I believe the answer is:
swell
'great' is the definition.
(I know that great can be written as swell)
'squadron leader with skill' is the wordplay.
'leader' indicates taking the first letters.
'with skill' becomes 'well' (I've seen this in another clue).
The initial letter of 'squadron' is 's'.
's'+'well'='SWELL'
(Other definitions for swell that I've seen before include "Enlarge; sea movement" , "blowing top" , "Become larger like toff" , "Enlarge; excellent" , "Balloon - movement of the sea's surface" .)