Catch a percentage, half of nets hauled up (6)
I believe the answer is:
entrap
'catch' is the definition.
(to entrap is to catch with a trap)
'a percentage half of nets hauled up' is the wordplay.
'a percentage' becomes 'part' ('part' can be a synonym of 'percentage').
'half of' means to take half the letters.
'hauled up' is a reversal indicator.
'nets' cut in half is 'ne'.
'part'+'ne'='partne'
'partne' reversed gives 'ENTRAP'.
(Other definitions for entrap that I've seen before include "Set up" , "net" , "Deceive -- lead on" , "Frame -- stitch up" , "Trick or beguile for parent" .)