Fragile weakling, initially, looking game (5)
I believe the answer is:
wispy
'fragile' is the definition.
(thesaurus)
'weakling initially looking game' is the wordplay.
'initially' says to take the initial letters.
'looking game' becomes 'ispy' (I've seen this before).
The first letter of 'weakling' is 'w'.
'w'+'ispy'='WISPY'
(Other definitions for wispy that I've seen before include "Straggly" , "Slender and delicate" , "Light and fine in texture" , "In thin strands" , "Diaphanous" .)