Tree-dwelling boar possibly genuine (8)
I believe the answer is:
arboreal
'tree-dwelling' is the definition.
(I've seen this in another clue)
'boar possibly genuine' is the wordplay.
'possibly' indicates anagramming the letters.
'genuine' becomes 'real' (similar in meaning).
'boar' anagrammed gives 'arbo'.
'arbo'+'real'='ARBOREAL'
(Other definitions for arboreal that I've seen before include "Relating to trees" , "Living among trees" , "living in forest" , "found in branches" , "Tree-dwelling" .)