Crossword Genius

Scent hard work writing out a verse (5)

Ross

I believe the answer is:

trail

I'm a little stuck... Click here to teach me more about this clue!

'scent' is the definition.
(I've seen this before)

'hard work writing out a verse' is the wordplay.
I cannot really see how this works, but
'writing' could be 'r' (one of the traditional three R's of education) and 'r' is found in the answer.
'a' is within the answer.
The remaining letters 'til' is a valid word which might be clued in a way I don't see.
This may be the basis of the clue (or it may be nonsense).

Can you help me to learn more?

(Other definitions for trail that I've seen before include "Spoor - lag behind" , "advertise upcoming programmes" , "Get behind" , "Wake" , "Forest path" .)

I've seen this clue in The Times.
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