Colour match in enclosure
I believe the answer is:
pea green
'colour' is the definition.
(I've seen this before)
'match in enclosure' is the wordplay.
'match' becomes 'agree' ('agree' can be a synonym of 'match'**).
'in' indicates putting letters inside.
'enclosure' becomes 'pen' (pen is a kind of enclosure).
'agree' inserted inside 'pen' is 'PEA-GREEN'.
(Other definitions for pea green that I've seen before include "Bright colour with a yellow tinge - eager pen (anag)" , "Vegetable shade?" , "Bright vegetable colour" , "Bright colour (of vegetables)" , "Colour of Owl and Pussycat's boat (Lear)" .)