British unit travelled one mile in April (8)
I believe the answer is:
imperial
'british' is the definition.
Both the answer and definition are adjectives. Maybe there's an association between them I don't understand?
'unit travelled one mile in april' is the wordplay.
I cannot really see how this works, but
'unit' could be 'rial' (rial is a kind of unit) and 'rial' is located in the answer.
'one' could be 'i' (Roman numeral) and 'i' is found within the answer.
'mile' could be 'm' (common abbreviation) and 'm' is found within the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for imperial that I've seen before include "Sovereign - old Russian gold coin - type of beard" , "Supreme, august; a beard" , "Related to empire" , "Magnificent; mint --" , "Relating to empire" .)