Stop — you're heard last (6)
I believe the answer is:
endure
'heard last' is the definition.
'endure' can be an answer for 'last' (I've seen this before). I'm not sure about the 'heard' bit.
'stop you're' is the wordplay.
'stop' becomes 'end' (synonyms).
'you're' becomes 'ure' (I can't explain this - if you can you should give a lot more credence to this answer).
'end'+'ure'='ENDURE'
Can you help me to learn more?
(Other definitions for endure that I've seen before include "Bear, suffer" , "Persist over time" , "Tolerate, put up with" , "Suffer or undergo" , "Stand" .)