Record temperature, record American rejected (4)
I believe the answer is:
tape
'record' is the definition.
(I know that record can be written as tape)
'temperature record american rejected' is the wordplay.
'temperature' becomes 't' (abbreviation).
'record' becomes 'EP' (abbreviation for extended play record).
'american' becomes 'a' (common abbreviation - e.g. in organisation names).
'rejected' says the letters should be written in reverse.
'ep'+'a'='epa'
'epa' reversed gives 'ape'.
't'+'ape'='TAPE'
(Other definitions for tape that I've seen before include "This is often stretched across the finishing line of race" , "Band" , "Binder" , "Record; material strip" , "Fabric strip; record" .)