Bury an indefinite number put in prison (6)
I believe the answer is:
intern
'put in prison' is the definition.
(I've seen this before)
'bury an indefinite number' is the wordplay.
'bury' becomes 'inter' (I've seen this before).
'an indefinite number' becomes 'n' (I've seen this in other clues).
'inter'+'n'='INTERN'
(Other definitions for intern that I've seen before include "to keep under lock and key" , "Medical graduate trainee" , "Official language of Pakistan" , "Imprison (eg, alien) as a precautionary measure" , "Detain in custody" .)