River bird makes one feel sorry (6)
I believe the answer is:
regret
'one feel sorry' is the definition.
(I've seen this before)
'river bird' is the wordplay.
'river' becomes 'r'.
'bird' becomes 'egret' (egret is a kind of bird**).
'r'+'egret'='REGRET'
'makes' is the link.
(Other definitions for regret that I've seen before include "Contrition" , "Deprecate" , "Remorse for something done or left undone" , "Rue, repine" , "Mourn" .)