South, if not cloud-covered (7)
I believe the answer is:
sunless
'cloud-covered' is the definition.
(synonyms)
'south if' is the wordplay.
'south' becomes 's' (abbreviation).
'if' becomes 'unless' (I've seen this before).
's'+'unless'='SUNLESS'
'not' acts as a link.
(Other definitions for sunless that I've seen before include "Dull" , "grey" , "Unlit by solar light" , "Offering nothing for a tanner" , "dark" .)