Can't make this point strongly enough - this could break your heart (6)
I believe the answer is:
stress
'can't make this point strongly enough this could break your heart' is the definition.
'stress' can be an answer for 'point' (thesaurus). I am not certain of the remainder of the definition.
'can't make this point' is the wordplay.
I cannot quite understand how this works, but
'point' could be 's' (S is an example) and 's' is found within the answer.
The remaining letters 'tress' is a valid word which might be clued in a way I don't understand.
This may be the basis of clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for stress that I've seen before include "Highlight" , "'Worry, pressure (6)'" , "Emphasise the pressure" , "Tension - accent" , "why off work?" .)