Windless and cold over Harlem occasionally (4)
I believe the answer is:
calm
'windless' is the definition.
(similar in meaning)
'cold over harlem occasionally' is the wordplay.
'cold' becomes 'C' (eg on taps).
'over' says to put letters next to each other.
'occasionally' means one should take alternating letters (letters taken at regular intervals or occasions).
The alternate letters of 'harlem' are 'alm'.
'c'+'alm'='CALM'
'and' acts as a link.
(Other definitions for calm that I've seen before include "Unruffled, not excited" , "'After a storm comes a ....'" , "Cool, composed" , "Placid, unexcited" , "Tranquil, undisturbed" .)