Agency worker takes age making paint (7)
I believe the answer is:
tempera
'paint' is the definition.
(type of paint)
'agency worker takes age' is the wordplay.
'agency worker' becomes 'temp' (temporary worker sent from an agency).
'takes' says to put letters next to each other.
'age' becomes 'era' (both can mean a long time).
'temp'+'era'='TEMPERA'
'making' is the link.
(Other definitions for tempera that I've seen before include "Means of painting - pet mare (anag)" , "Method of drawing" , "Egg-yolk and water painting medium" , "Emulsion paint" , "Type of paint" .)