Investigates tense gangster finding religious office (10)
I believe the answer is:
priesthood
'religious office' is the definition.
'investigates tense gangster' is the wordplay.
'investigates tense' becomes 'priest' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'gangster' becomes 'hood' (I've seen this before).
'priest'+'hood'='PRIESTHOOD'
'finding' is the link.
Can you help me to learn more?
(Other definitions for priesthood that I've seen before include "Minister's office" , "cleric's office" , "office in church" , "future for seminarian" , "Ordained order" .)