Jeer, getting heated about nothing (4)
I believe the answer is:
hoot
'jeer' is the definition.
(thesaurus)
'heated about nothing' is the wordplay.
'heated' becomes 'hot' ('hot' can be a synonym of 'heated').
'about' means one lot of letters goes inside another.
'nothing' becomes 'o' (looks like zero - 0).
'hot' going around 'o' is 'HOOT'.
'getting' acts as a link.
(Other definitions for hoot that I've seen before include "Owl's call" , "Owl's cry" , "what's voiced in parliament?" , "Hollow cry" , "Sound of owl" .)