Labour aim always to be heard (9)
I believe the answer is:
endeavour
'labour' is the definition.
(endeavour can mean a labour or effort)
'aim always to be heard' is the wordplay.
I cannot really see how this works, but
'aim' could be 'end' (both can mean a goal or purpose) and 'end' is located in the answer.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for endeavour that I've seen before include "hard work" , "Morse" , "Make a serious effort" , "Industrious effort" , "Try hard (to achieve)" .)