A pie's possibly a nice warm colour (5)
I believe the answer is:
sepia
'nice warm colour' is the definition.
'sepia' can be an answer for 'colour' (sepia is a kind of colour). I'm unsure of the 'nice warm' bit.
'a pie's possibly a' is the wordplay.
'possibly' is an anagram indicator.
'pies' is an anagram of 'sepi'.
'sepi'+'a'='SEPIA'
Can you help me to learn more?
(Other definitions for sepia that I've seen before include "Brown pigment produced from cuttlefish ink" , "Pigment got from cuttlefish ink" , "Brownish tone associated with old photographs" , "Colour of old photographs" , "Brownish tint or pigment" .)