Mercian king to hold out for hearing (4)
I believe the answer is:
offa
'mercian king' is the definition.
(I've seen this before)
'hold out for hearing' is the wordplay.
'hold out' becomes 'offer' (I've seen this before).
'for hearing' indicates a 'sounds like' (homophone) clue.
'offer' is a homophone of 'OFFA'.
'to' acts as a link.
(Other definitions for offa that I've seen before include "Dividing wall builder" , "Mercian leader" , "King of Mercia, who may have built a dyke" , "Who ditched England and Wales" , "Old dyke builder, d. 796" .)