A commercial, alternatively, featuring male singer in rep (10)
I believe the answer is:
ambassador
'rep' is the definition.
(a country's representative)
'a commercial alternatively featuring male singer' is the wordplay.
'commercial' becomes 'ad' (abbreviation for advertisement).
'alternatively' becomes 'or'.
'featuring' indicates putting letters inside.
'male' becomes 'm' (common abbreviation).
'singer' becomes 'bass' (bass is a kind of singer).
'a'+'ad'+'or'='aador'
'm'+'bass'='mbass'
'aador' going around 'mbass' is 'AMBASSADOR'.
'in' acts as a link.
(Other definitions for ambassador that I've seen before include "Overseas diplomat" , "Messenger" , "delegate" , "diplomatic type" , "In a different case, he could be" .)