Half parses this clue, having noted the number beforehand in coffee break (9)
I believe the answer is:
elevenses
'coffee break' is the definition.
(I've seen this before)
'half parses this clue having noted the number beforehand' is the wordplay.
I cannot quite understand how this works, but
'number' could be 'eleven' (eleven is a kind of number) and 'eleven' is present in the answer.
The remaining letters 'ses' is a valid word which might be clued in a way I don't see.
This may be the basis of the clue (or it may be nonsense).
'in' is the link.
Can you help me to learn more?
(Other definitions for elevenses that I've seen before include "Soccer teams" , "Mid-morning refreshment" , "tenses found immediately before this?" , "energy getting second break" , "Mid-morning snacks" .)