Feel unusually frail (5)
I believe the answer is:
flair
'feel' is the definition.
(thesaurus)
'unusually frail' is the wordplay.
'unusually' is an anagram indicator.
'frail' with letters rearranged gives 'FLAIR'.
(Other definitions for flair that I've seen before include "skill" , "Elan; panache" , "Natural talent or panache" , "Stylishness; talent" , "Natural ability to do something well (5)" .)