Unfortunate pals she mistreated (7)
I believe the answer is:
hapless
'unfortunate' is the definition.
(similar in meaning)
'pals she mistreated' is the wordplay.
'mistreated' indicates an anagram.
'pals'+'she'='palsshe'
'palsshe' anagrammed gives 'HAPLESS'.
(Other definitions for hapless that I've seen before include "Ill-fated" , "Unlucky, unfortunate" , "Unfortunate, wretched" , "Ill-starred" , "Piteous" .)