Covered by hemispherical vault, told to become a doctor (5)
I believe the answer is:
domed
'covered' is the definition.
Both the answer and definition are adjectives. Perhaps there's an association between them I don't understand?
'hemispherical vault told to become a doctor' is the wordplay.
I cannot quite understand how this works, but
'vault' could be 'dome' (I've seen this in another clue) and 'dome' is found in the answer.
'doctor' could be 'd' (eg in PhD, Doctor of Philosophy) and 'd' is found in the answer.
This accounts for all the letters.
This may be the basis of the clue (or it may be nonsense).
'by' is the link.
Can you help me to learn more?
(Other definitions for domed that I've seen before include "not flat!" , "Shaped like rounded roof" , "Vaulted" , "cupola" , "with a meniscus" .)