Airmen soaring, circling Italy, having good weather (4)
I believe the answer is:
'having good weather' is the definition.
(as in fair weather)
'airmen soaring circling italy' is the wordplay.
'airmen' becomes 'RAF' (Royal Air Force).
'soaring' shows that the letters should be reversed in order (in a down clue, letters 'soar' up).
'circling' is an insertion indicator (circling can mean going around or containing).
'italy' becomes 'i'.
'raf' in reverse letter order is 'far'.
'far' enclosing 'i' is 'FAIR'.
(Other definitions for fair that I've seen before include "Free from discrimination" , "Sign following Pisces" , "'Just, meet (4)'" , "Equitable - market - not bad" , "(Of skin) pale" .)