Cooler yellowish brown, off-white (3)
I believe the answer is:
fan
'cooler' is the definition.
(something which cools)
'yellowish brown off-white' is the wordplay.
'yellowish brown' becomes 'fawn' (I've seen this in another clue).
'off' suggests deleting specific letters ('off' can mean to remove).
'white' becomes 'w'.
'fawn' with 'w' taken out is 'FAN'.
(Other definitions for fan that I've seen before include "Manually wielded cooling device" , "Aficionado" , "Spanish women wave it to cool themselves" , "Ardent admirer" , "Great enthusiast" .)