Horse somewhere in East Anglia one associated with Judy (7,5)
I believe the answer is:
suffolk punch
'horse' is the definition.
(I've seen this before)
'somewhere in east anglia one associated with judy' is the wordplay.
'somewhere in east anglia' becomes 'Suffolk' (Suffolk is a county in East Anglia).
'one associated with judy' becomes 'Punch' (as in Punch and Judy shows).
'suffolk'+'punch'='SUFFOLK PUNCH'
(Other definitions for suffolk punch that I've seen before include "One helping to deliver drink" , "Aldeburgh festival?" , "horse" .)