A very hard worker, the letter said (3)
I believe the answer is:
bee
'a very hard worker' is the definition.
'bee' can be an answer for 'worker' (a worker bee). I am not sure about the 'a very hard' bit.
'the letter said' is the wordplay.
'the letter' becomes 'b'.
'said' shows a homophone (sound like).
'b' sounds like 'BEE'.
Can you help me to learn more?
(Other definitions for bee that I've seen before include "Honey producer" , "Flying insect (often busy)" , "Busy buzzer" , "Hymenopterous insect" , "Honey-making insect" .)