Indian, perhaps Apache, finally put in old prison (5)
I believe the answer is:
ocean
'indian perhaps' is the definition.
(Indian Ocean is an example)
'apache finally put in old prison' is the wordplay.
'finally' indicates one should take the final letters.
'put in' is an insertion indicator.
'old' becomes 'o' (common abbreviation eg in OE for Old English).
'prison' becomes 'can' (the can is American slang for prison).
The final letter of 'apache' is 'e'.
'o'+'can'='ocan'
'e' inserted inside 'ocan' is 'OCEAN'.
(Other definitions for ocean that I've seen before include "eg Arctic" , "Big sea" , "Vast sea" , "eg Indian, Atlantic" , "Large expanse of sea" .)