Have the U in USA large, as is customary (5)
I believe the answer is:
usual
'is customary' is the definition.
(similar in meaning)
'have the u in usa large' is the wordplay.
I cannot really see how this works, but
'u' is found in the answer.
an anagram of 'usa' is 'sua' which is within the answer.
'large' could be 'l' (eg in clothes sizes) and 'l' is located in the answer.
This accounts for all the letters.
This may be the basis of the clue (or it may be nonsense).
'as' acts as a link.
Can you help me to learn more?
(Other definitions for usual that I've seen before include "Conventional" , "Normal, customary" , "In accordance with regular practice" , "not rum?" , "Customary, routine" .)