One's inclined to use admin in building (12)
I believe the answer is:
mountainside
'one's inclined' is the definition.
(I've seen this before)
'to use admin in building' is the wordplay.
'building' indicates anagramming the letters.
'to'+'use'+'admin'+'in'='touseadminin'
'touseadminin' anagrammed gives 'MOUNTAINSIDE'.
(Other definitions for mountainside that I've seen before include "Big hill slope" , "It isn't flat" , "where many adventurous explorers go?" , "One's inclined" , "Incline" .)