Related Clues:
- Requiring hard work
- Fatiguing (task)
- Steep; laborious
- What a tough course can be
- A marathon course can be this
- A tough marathon course will be this
- Hard duke's reportedly dubious following
- Difficult road with sharp bend - that's nothing, in Oz!
- Demanding princess, very noisy one, joining sect
- Difficult, tiring
- Not easy to find couple in a hurry — husband's gone off
- Tricky, like Boyd's youth
- Extremely taxing
- Pair participating in a short run that's tiring
- Requesting