Modesty of fling with head (7)
I believe the answer is:
shyness
'modesty' is the definition.
(thesaurus)
'fling with head' is the wordplay.
'fling' becomes 'shy' (shy can mean to throw).
'with' says to put letters next to each other.
'head' becomes 'ness' (both can mean a promontory).
'shy'+'ness'='SHYNESS'
'of' is the link.
(Other definitions for shyness that I've seen before include "Reserve" , "Bashfulness" , "Diffidence" , "lack of confidence" , "Nervousness, timidity" .)