A large number; doesn't matter which large number (4)
I believe the answer is:
many
'large number' is the definition.
(many means lots of something)
'a large number doesn't matter' is the wordplay.
I cannot really see how this works, but
'a' could be 'an' and 'an' is present in the answer.
'number' could be 'm' (M is an example) and 'm' is found in the answer.
'matter' could be 'y' (Y is an example) and 'y' is found in the answer.
This accounts for all the letters.
This may be the basis of the clue (or it may be nonsense).
'which' is the link.
Can you help me to learn more?
(Other definitions for many that I've seen before include "multitude" , "Lots" , "Several" , "legion" , "A lot of" .)