Reserve break in Crete supported by church (9)
I believe the answer is:
reticence
'reserve' is the definition.
('reticence' can be a synonym of 'reserve')
'break in crete supported by church' is the wordplay.
'break' is an anagram indicator.
'supported by' means one lot of letters go next to another (letters go below - in down clue).
'church' becomes 'ce' (abbreviation for Church of England).
'in'+'crete'='increte'
'increte' anagrammed gives 'reticen'.
'reticen'+'ce'='RETICENCE'
(Other definitions for reticence that I've seen before include "'Reserve, taciturnity (9)'" , "Tendency to hold back" , "Restraint" , "Quality of being sparing in communication" , "Shyness" .)