A student painting outdoors (8)
I believe the answer is:
alfresco
'outdoors' is the definition.
(synonyms)
'a student painting' is the wordplay.
'student' becomes 'l' (as in L-plates for learner drivers).
'painting' becomes 'fresco' (fresco is a kind of painting).
'a'+'l'+'fresco'='ALFRESCO'
(Other definitions for alfresco that I've seen before include "Located outdoors" , "Out of doors" , "exposed to the fresh air" , "Open-air" , "Meal eaten in the outdoors" .)