Pesky kid torments politician for a joke (6,3,5)
I believe the answer is:
shaggy dog story
'joke' is the definition.
(shaggy dog story is a kind of joke)
'pesky kid torments politician for a' is the wordplay.
I cannot quite see how this works, but
'politician' could be 'tory' (term for a Conservative Party politician) and 'tory' is found in the answer.
'a' is present in the answer.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for shaggy dog story that I've seen before include "woolly tale?" , "Beardie's tale" , "It's long and anticlimactic" , "joke finally ending weakly" , "silly joke" .)