Need large one before retiring (6)
I believe the answer is:
entail
'need' is the definition.
(entail means to require or give rise to)
'large one before retiring' is the wordplay.
I cannot really understand how this works, but
'large' could be 'l' (eg in clothes sizes) and 'l' is found within the answer.
'one' could be 'i' (Roman numeral) and 'i' is located in the answer.
'before' could be 'e' (I've seen this in other clues) and 'e' is found in the answer.
This may be the basis of the clue (or it may be nonsense).
(Other definitions for entail that I've seen before include "Cut" , "Involve or make necessary" , "Call for" , "Occasion" , "Involve or require" .)