Modestly having a fling at the ultimate Aunt Sally (5)
I believe the answer is:
shyly
'modestly' is the definition.
Both the definition and answer are adverbs. Maybe you can see a link between them that I can't see?
'a fling at the ultimate aunt sally' is the wordplay.
'a fling' becomes 'shy' (shy can mean to throw).
'at' says to put letters next to each other.
'the ultimate aunt sally' becomes 'ly' (I am not sure about this - if you are sure you should believe this answer much more).
'shy'+'ly'='SHYLY'
'having' acts as a link.
Can you help me to learn more?
(Other definitions for shyly that I've seen before include "In a timid manner" , "Nervously, timidly" , "In reserved way" .)