Broadcaster’s raised promotion after he’s become materialist (9)

'materialist' is the definition.
(someone obsessed with material wealth)

'broadcaster's raised promotion after he's' is the wordplay.
'broadcaster's' indicates a 'sounds like' (homophone) clue (how it might sound on a broadcast).
'raised' becomes 'bred' (eg bred children).
'promotion' becomes 'ad' (short for advert).
'after' means one lot of letters go next to another.
'bred' is a homophone of 'bread'.
'ad' after 'he' is 'head'.
'bread'+'head'='BREADHEAD'

'become' is the link.