We’re told a competitor’s coming (7)
I believe the answer is:
arrival
'coming' is the definition.
(I know that coming can be written as arrival)
'we're told a competitor's' is the wordplay.
'we're told' indicates a 'sounds like' (homophone) clue.
'competitor' becomes 'rival' (synonyms).
'a'+'rival'='arival'
'arival' is a homophone of 'ARRIVAL'.
(Other definitions for arrival that I've seen before include "Act of coming" , "Coming - comer" , "Attainment of destination" , "Appearance (at a place)" , "Advent" .)