American needing time for treatment (5)
I believe the answer is:
usage
'treatment' is the definition.
(thesaurus)
'american needing time for' is the wordplay.
'american' becomes 'us'.
'needing' means one lot of letters go next to another.
'time for' becomes 'age' (I've seen this in other clues).
'us'+'age'='USAGE'
(Other definitions for usage that I've seen before include "Accepted or habitual practice" , "Common practice" , "etiquette" , "Application" , "Treatment, practice" .)