It heartens seafarers a great deal (3)
I believe the answer is:
far
'a great deal' is the definition.
Both the answer and definition are adverbs. Maybe they are linked in a way I don't understand?
'it heartens seafarers' is the wordplay.
'FAR' is hidden in amongst the letters.
But, I'm not sure how the hidden word is indicated.
Can you help me to learn more?
(Other definitions for far that I've seen before include "Distant" , "Very much" , "A long, long way to go" , "Remote" , "At a great distance way" .)