Holding volume, in Irish, upside down (7)
I believe the answer is:
inverse
'upside down' is the definition.
(I've seen this before)
'holding volume in irish' is the wordplay.
'holding' is an insertion indicator.
'volume' becomes 'v'.
'irish' becomes 'erse' (I've seen this before).
'in'+'erse'='inerse'
'v' put within 'inerse' is 'INVERSE'.
(Other definitions for inverse that I've seen before include "Upside down - opposite in effect" , "Opposite in direction" , "Reversed in position like enviers" , "Contrary in effect" , "Opposite (like poetry?)" .)