Don't play the old man — ’e kept giving very unwelcome advice (4,4)
I believe the answer is:
drop dead
'don't play the old man 'e kept giving very unwelcome advice' is the definition.
I can't tell whether this definition defines the answer.
'don't play the old man 'e kept' is the wordplay.
'don't play' becomes 'drop' (I can't explain this - if you can you should believe this answer much more).
'the old man' becomes 'dad' (both can mean one's father).
'kept' means one lot of letters goes inside another.
'dad' placed around 'e' is 'dead'.
'drop'+'dead'='DROP-DEAD'
Can you help me to learn more?
(Other definitions for drop dead that I've seen before include "Absolutely (gorgeous)" , "Rude injunction to fall lifeless" , "Really offensive remark" , "to appear so gorgeous" , "Suddenly fail" .)