Ape is strange colour (5)
I believe the answer is:
sepia
'colour' is the definition.
(sepia is a kind of colour)
'ape is strange' is the wordplay.
'strange' is an anagram indicator.
'ape'+'is'='apeis'
'apeis' is an anagram of 'SEPIA'.
(Other definitions for sepia that I've seen before include "Sort of drawing" , "brownish colour" , "Reddish brown -- ie sap (anag)" , "Old drawing" , "Dark reddish-brown pigment" .)