Prohibit company banking money (5)
I believe the answer is:
banco
'prohibit company banking money' is the definition.
(I've seen this before)
'prohibit company' is the wordplay.
'prohibit' becomes 'ban' (banning is a kind of prohibiting).
'company' becomes 'co' (abbreviation).
'ban'+'co'='BANCO'
(Other definitions for banco that I've seen before include "Game" , "Prohibit company banking money" .)