Vain academic engaged by university board (12)
I believe the answer is:
unprofitable
'vain' is the definition.
(I've seen this before)
'academic engaged by university board' is the wordplay.
'academic' becomes 'prof'.
'engaged by' means one lot of letters goes inside another (I've seen this in other clues).
'university' becomes 'uni' (I've seen this in other clues).
'board' becomes 'table' ('table' can be a synonym of 'board'**).
'prof' going inside 'uni' is 'unprofi'.
'unprofi'+'table'='UNPROFITABLE'
(Other definitions for unprofitable that I've seen before include "Not beneficial" , "Vain" .)