Whinger to cry, frightfully embarrassing (12)
I believe the answer is:
cringeworthy
'embarrassing' is the definition.
(I've seen this before)
'whinger to cry frightfully' is the wordplay.
'frightfully' is an anagram indicator.
'whinger'+'to'+'cry'='whingertocry'
'whingertocry' is an anagram of 'CRINGEWORTHY'.
(Other definitions for cringeworthy that I've seen before include "Acutely embarrassing" , "Causing embarrassment" , "Severely embarrassing" .)