Sidekick shot Mickey Mouse (6)
I believe the answer is:
paltry
'mickey mouse' is the definition.
(thesaurus)
'sidekick shot' is the wordplay.
'sidekick' becomes 'pal' ('pal' can be a synonym of 'sidekick').
'shot' becomes 'try' (I've seen this in other clues).
'pal'+'try'='PALTRY'
(Other definitions for paltry that I've seen before include "Mean - trifling" , "not worth considering" , "Minor, insignificant" , "Feeble" , "Petty - trifling" .)