The bird upsets Ron a lot (7)
I believe the answer is:
ortolan
'the bird' is the definition.
(ortolan is a kind of bird)
'upsets ron a lot' is the wordplay.
'upsets' indicates an anagram.
'ron'+'a'+'lot'='ronalot'
'ronalot' anagrammed gives 'ORTOLAN'.
(Other definitions for ortolan that I've seen before include "European bunting" , "Type of bunting eaten as a delicacy" , "high-flying singer" , "Small songbird" , "Bobolink" .)