Cruel guys Tom’s mistaken for bad people (4,9)
I believe the answer is:
ugly customers
'bad people' is the definition.
(informal term for nasty people)
'cruel guys tom's mistaken' is the wordplay.
'mistaken' indicates an anagram.
'cruel'+'guys'+'toms'='cruelguystoms'
'cruelguystoms' with letters rearranged gives 'UGLY CUSTOMERS'.
'for' acts as a link.
(Other definitions for ugly customers that I've seen before include "Dangerous antagonists" , "must trouble a beautician" .)