By ten to one the vehicle must be back: he’s very strict (8)
I believe the answer is:
martinet
'by ten to one the vehicle must be back he's very strict' is the definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
'by ten to one the vehicle must be back he's' is the wordplay.
I cannot really understand how this works, but
an anagram of 'ten' is 'net' which is located in the answer.
'one' could be 'i' (Roman numeral) and 'i' is located in the answer.
'he' could be 'mart' and 'mart' is present in the answer.
This accounts for all the letters.
This may be the basis of clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for martinet that I've seen before include "A rigorous operator" , "'Disciplinarian, exacts strict conformity to rules (8)'" , "General" , "Strict disciplinarian - met train (anag)" , "A strict disciplarian" .)