L, M or S on garment? You've got it right! (5,3,4,2,2)
I believe the answer is:
thats the size of it
'l m' is the definition.
I don't know anything about this answer so I can't tell whether this works.
's on garment? you've got it right' is the wordplay.
I cannot really understand how this works, but
's' could be 'es' (es or ess is the spelling of the letter's name) and 'es' is found within the answer.
'on' could be 'at' (I've seen this in other clues) and 'at' is found in the answer.
'it' could be 't' (abbreviation. e.g. in 'tis) and 't' is located in the answer.
'right' could be 'fit' (I've seen this in another clue) and 'fit' is found in the answer.
This explanation may well be incorrect...
'or' is the link.
Can you help me to learn more?
(Other definitions for thats the size of it that I've seen before include "What's said after measuring" , "It's a true assessment" .)