Better a large size, by the sound of it (5)
I believe the answer is:
excel
'better' is the definition.
(excel can mean to better or beat)
'a large size by the sound of it' is the wordplay.
I cannot really see how this works, but
'large' could be 'l' (eg in clothes sizes) and 'l' is found in the answer.
'by' could be 'x' (2 by 4 is 2 x 4) and 'x' is found in the answer.
'it' could be 'e' ('e' can mean 'electronic' which is similar to 'IT') and 'e' is located in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for excel that I've seen before include "Do exceedingly well" , "surpass all others" , "Be exceptionally good (at something)" , "Distinguish oneself - XL" , "Perform outstandingly well" .)