Cooler frost initially seen on hilltop (6)
I believe the answer is:
fridge
'cooler' is the definition.
(I've seen this before)
'frost initially seen on hilltop' is the wordplay.
'initially' suggests taking the first letters.
'seen on' says to put letters next to each other.
'hilltop' becomes 'ridge' (I've seen this before).
The first letter of 'frost' is 'f'.
'f'+'ridge'='FRIDGE'
(Other definitions for fridge that I've seen before include "Cooler in kitchen" , "Cooling cabinet (abbr)" , "A domestic appliance" , "Food cooler" .)