Beast the solver heard (3)
I believe the answer is:
ewe
'beast' is the definition.
(I've seen this before)
'solver heard' is the wordplay.
'solver' becomes 'you' (the person solving the crossword).
'heard' shows a homophone (sound like).
'you' is a homophone of 'EWE'.
'the' is the link.
(Other definitions for ewe that I've seen before include "Female ovine" , "21a [SHEEP]" , "Scottish loch" , "Female animal" , "She'll provide material to knit" .)