'That OK then?' Lad rudely: 'I'm not interested!' (4,2,3,4)
I believe the answer is:
talk to the hand
'i'm not interested' is the definition.
I know nothing about this answer so I can't tell whether it can be defined by this definition.
'that ok then? lad rudely' is the wordplay.
'rudely' is an anagram indicator (rude can mean rough or unrefined).
'that'+'ok'+'then'+'lad'='thatokthenlad'
'thatokthenlad' is an anagram of 'TALK TO THE HAND'.
Can you help me to learn more?
(Another definition for talk to the hand that I've seen is " scornful response".)