Foolish getting involved in dust-up: idiotic (6)
I believe the answer is:
stupid
'foolish' is the definition.
('stupid' can be a synonym of 'foolish')
'involved in dust-up idiotic' is the wordplay.
'involved in' indicates a hidden word.
'STUPID' can be found hidden inside 'dust up idiotic'.
'getting' is the link.
(Other definitions for stupid that I've seen before include "Lacking wit or intelligence" , "Crass" , "(Seeming to be) lacking intelligence" , "Ignorant" , "potty" .)