Yellowish-green colour (5)
I believe the answer is:
olive
'yellowish-green colour' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for olive that I've seen before include "Bitter fruit" , "woman" , "Oily stone fruit" , "Oil-yielding tree" , "One [TYPE OF TREE] is from the Mediterranean" .)