The brownish colour of an ortanique (3)
I believe the answer is:
tan
'the brownish colour' is the definition.
(I've seen this before)
'of an ortanique' is the wordplay.
'of' indicates the answer is hidden within the clue.
'TAN' is hidden in the letters of 'ortanique'.
(Other definitions for tan that I've seen before include "Process" , "Nice brown induced by sun" , "Yellow-brown colour" , "Turn hide into leather" , "Sun-kissed" .)