By which ploughmen steer a straight course? (7)
I believe the answer is:
tillers
'by which ploughmen steer a straight' is the definition.
I can't judge whether this defines the answer.
'course?' is the wordplay.
I cannot really understand how this works, but
'course?' could be 's' and 's' is located in the answer.
The remaining letters 'tiller' is a valid word which might be clued in a way I don't see.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for tillers that I've seen before include "gardeners" , "Steering bars" , "Levers to turn rudders" .)