Clerical order looks into East End gangster (10)
I believe the answer is:
priesthood
'clerical order' is the definition.
(thesaurus)
'looks into east end gangster' is the wordplay.
'looks into' becomes 'pries' (I can't justify this - if you can you should believe this answer much more).
'end' says to take the final letters.
'gangster' becomes 'hood' (I've seen this in another clue).
The final letter of 'east' is 't'.
'pries'+'t'+'hood'='PRIESTHOOD'
Can you help me to learn more?
(Other definitions for priesthood that I've seen before include "future for seminarian" , "Ordained order" , "Minister's office" , "office in church" , "cleric's office" .)