Second very old church to support Bismarck, perhaps very quietly (5,4)
I believe the answer is:
sotto voce
'very quietly' is the definition.
(I've seen this before)
'second very old church to support bismarck perhaps' is the wordplay.
'second' becomes 's' (common abbreviation).
'very old' becomes 'vo' (this might be a standard abbreviation which I don't know about).
'church' becomes 'ce' (abbreviation for Church of England).
'to support' means one lot of letters go next to another (in a down clue, some letters hold others up).
'bismarck perhaps' becomes 'otto' (Otto von Bismarck is an example).
'vo'+'ce'='voce'
'voce' after 'otto' is 'ottovoce'.
's'+'ottovoce'='SOTTO VOCE'
Can you help me to learn more?
(Other definitions for sotto voce that I've seen before include "In an undertone, from Italian" , "Like subdued talking" , "on the quiet" , "In an undertone from Italy" , "Speaking quietly" .)