After a poor start, it may yield coal (3)
I believe the answer is:
pit
'yield coal' is the definition.
The answer and definition can be both natural objects as well as being singular nouns.
Maybe they are linked in a way I don't understand?
'after a poor start it' is the wordplay.
'after' is a charade indicator (letters next to each other).
'start' says to take the initial letters.
The initial letter of 'poor' is 'p'.
'p' next to 'it' is 'PIT'.
'may' is the link.
Can you help me to learn more?
(Other definitions for pit that I've seen before include "Tip into crater" , "Large hole; mine" , "Hollow" , "Match (one's wits); mine" , "Coal mine" .)