Frost's heard what Frost wrote (5)
I believe the answer is:
rhyme
'frost wrote' is the definition.
I can't judge whether this definition defines the answer.
'frost's heard' is the wordplay.
'frost' becomes 'rime' (rime is a type of frost).
'heard' shows a homophone (sound like).
'rime' is a homophone of 'RHYME'.
'what' acts as a link.
Can you help me to learn more?
(Other definitions for rhyme that I've seen before include "Short piece of verse" , "anticipated by a nursery perhaps" , "Without reason or . . . . . - makes no sense" , "Have identical terminal sounds" , "Charlie Farley for example?" .)