Transport firm collecting gold fabrication within hour (7)
I believe the answer is:
haulier
'transport firm' is the definition.
'collecting gold fabrication within hour' is the wordplay.
'collecting' indicates putting letters inside.
'gold' becomes 'au' (Au is the chemical symbol for gold).
'fabrication' becomes 'lie' (I've seen this before).
'within' is an insertion indicator.
'hour' becomes 'hr' ('hr' can be a synonym of 'hour').
'lie' inserted within 'hr' is 'hlier'.
'au' going within 'hlier' is 'HAULIER'.
(Other definitions for haulier that I've seen before include "Trucking company" , "Transporter of goods by road" , "He could transport" , "freight carrier" , "One transports goods in a vehicle" .)