Revealing container in farm building (6)
I believe the answer is:
scanty
'revealing' is the definition.
(I've seen this before)
'container in farm building' is the wordplay.
'container' becomes 'can' (can is a kind of container).
'in' is an insertion indicator.
'farm building' becomes 'sty'.
'can' going inside 'sty' is 'SCANTY'.
(Other definitions for scanty that I've seen before include "(Of clothing) barely adequate" , "Modest" , "Sparse, meagre" , "Give (to a good cause)" , "Spare" .)