Northern labourer caught creature eating fish (6)
I believe the answer is:
cotter
'northern labourer' is the definition.
(historical northern term for a farm labourer)
'caught creature eating fish' is the wordplay.
'caught' becomes 'c' (cricket abbreviation).
'creature eating fish' becomes 'otter' (otters eat fish).
'c'+'otter'='COTTER'
(Other definitions for cotter that I've seen before include "Small farmer in the Scottish Highlands" , "Scottish peasant" , "Pin or wedge for fastening and tightening" , "type of pin" .)