Bloke bound to hide one principal motive (10)
I believe the answer is:
mainspring
'motive' is the definition.
(I have seen 'Chief motive' mean 'mainspring' so perhaps 'motive' could also mean 'mainspring')
'bloke bound to hide one principal' is the wordplay.
I cannot quite understand how this works, but
'bound' could be 'spring' (both can mean to leap) and 'spring' is present in the answer.
'one' could be 'i' (Roman numeral) and 'i' is located in the answer.
'bloke' could be 'man' (informal term for a man) and 'man' is located in the remaining letters.
This accounts for all the letters.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for mainspring that I've seen before include "Chief motive" , "essential to watch" , "Principal agent of motivation" , "It motivates" , "Pining rams (anag.)" .)