Painter occupying gallery finally calling for oils? (5)
I believe the answer is:
rainy
'calling for oils?' is the definition.
(oilskins might be worn if it rains)
'painter occupying gallery finally' is the wordplay.
'painter' becomes 'RA' (member of the Royal Academy of Arts).
'occupying' becomes 'in' (to occupy a building is to live in it).
'finally' suggests the final letters.
The final letter of 'gallery' is 'y'.
'ra'+'in'+'y'='RAINY'
(Other definitions for rainy that I've seen before include "The day one saves for" , "Pluvial" , "Save your money for a . . . . . day - to buy an umbrella?" , "Drizzly" , "With water falling outside" .)