Rib and rib-tickling twit (9)
I believe the answer is:
birdbrain
'twit' is the definition.
The answer and definition can be both people as well as being singular nouns.
Perhaps you can see a link between them that I don't see?
'rib and rib-tickling' is the wordplay.
'rib and rib' anagrams to 'BIRDBRAIN'.
However, I am unsure how this is indicated.
Can you help me to learn more?
(Other definitions for birdbrain that I've seen before include "Twittering twit?" , "Fool" , "Stupid" , "Silly person (with sparrow's mind?)" .)