Hasty rascal finds us evil, sadly (9)
I believe the answer is:
impulsive
'hasty' is the definition.
(thesaurus)
'rascal finds us evil sadly' is the wordplay.
'rascal' becomes 'imp' (synonyms).
'finds' means one lot of letters go next to another.
'sadly' is an anagram indicator.
'us'+'evil'='usevil'
'usevil' with letters rearranged gives 'ulsive'.
'imp'+'ulsive'='IMPULSIVE'
(Other definitions for impulsive that I've seen before include "Done without forethought" , "Rash" , "Hot-headed" , "responding promptly" , "Acting without forethought" .)