Seize small catches (4)
I believe the answer is:
bags
'catches' is the definition.
(bagging is a kind of catching)
'seize small' is the wordplay.
'seize' becomes 'bag' ().
'small' becomes 's' (abbreviation - e.g. clothes size).
'bag'+'s'='BAGS'
(Other definitions for bags that I've seen before include "fashion accessories" , "Gets" , "Containers for carrying, informally plenty" , "Lots of" , "Criticises" .)