Barrack and Michelle ultimately getting huge backing (4)
I believe the answer is:
gibe
'barrack' is the definition.
(I know that barrack can be written as gibe)
'michelle ultimately getting huge backing' is the wordplay.
'ultimately' says to take the final letters.
'getting' means one lot of letters go next to another.
'huge' becomes 'big' (similar in meaning).
'backing' says the letters should be written backwards.
The last letter of 'michelle' is 'e'.
'e'+'big'='ebig'
'ebig' reversed gives 'GIBE'.
'and' is the link.
(Other definitions for gibe that I've seen before include "Barb, dig" , "Dig, or a barbed comment" , "Jeer, mock" , "Jeer, barb" , "A jeering remark" .)