At heart, many need to help out (4)
I believe the answer is:
amid
'at heart' is the definition.
I know nothing about this answer so I can't tell whether this works.
'many need to help out' is the wordplay.
I cannot quite see how this works, but
'many' could be 'm' (Roman numeral for a thousand) and 'm' is located in the answer.
'help' could be 'aid' (synonyms) and 'aid' is present in the remaining letters.
This accounts for all the letters.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for amid that I've seen before include "A dim sort of preposition" , "Among" , "In the course of" , "Surrounded by" , "In the thick of" .)