Spades I loaned mum (6)
I believe the answer is:
silent
'mum' is the definition.
(to keep mum can informally mean to stay silent)
'spades i loaned' is the wordplay.
'spades' becomes 's' (abbreviation in card games).
'loaned' becomes 'lent' ('lend' can be a synonym of 'loan').
's'+'i'+'lent'='SILENT'
(Other definitions for silent that I've seen before include "Strange and astonishing thing" , "as lead character in Psycho?" , "Taciturn" , "Listen in order to be quiet" , "Utterly quiet" .)