Reserve suite but confused about street briefly (10)
I believe the answer is:
substitute
'reserve' is the definition.
(synonyms)
'suite but confused about street briefly' is the wordplay.
'confused' is an anagram indicator.
'about' indicates putting letters inside.
'street briefly' becomes 'st' ('briefly' suggests an abbreviation).
'suite'+'but'='suitebut'
'suitebut' is an anagram of 'subitute'.
'subitute' placed around 'st' is 'SUBSTITUTE'.
(Other definitions for substitute that I've seen before include "Replacement" , "Stand-in" , "Stand in" , "deputy" , "Reserve" .)