Knock back drink around noon and have something to eat (7)
I believe the answer is:
'something to eat' is the definition.
(parsnip is a kind of food)
'knock back drink around' is the wordplay.
'knock' becomes 'rap' (synonyms).
'back' is a reversal indicator.
'drink around' becomes 'snip' (I can't justify this - if you can you should give a lot more credence to this answer).
'rap' back-to-front is 'par'.
'noon and have' acts as a link.
I am not very happy about this link. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for parsnip that I've seen before include "Plant with edible white root" , "A white root vegetable" , "Pale carrot-like vegetable" , "Spar pin (anag) - vegetable" , "Yellow root vegetable" .)