For instance soak heron (5)
I believe the answer is:
egret
'heron' is the definition.
(egret is a kind of heron)
'for instance soak' is the wordplay.
'for instance' becomes 'eg' ('e.g.' can be a synonym of 'for instance').
'soak' becomes 'ret' (retting is a kind of soaking).
'eg'+'ret'='EGRET'
(Other definitions for egret that I've seen before include "Stork-like bird" , "Type of forty eight Ac" , "White-feathered wading bird" , "young bird" , "Long-plumed heron" .)