My crossword dictionary gives 'SPLIT' as an alternative for 'CRACK', 'PART' and 'GAPE' so I guess that's it.
The one that I struggled with was 6D Suspect satanic rites, extreme ones, involved a churchman (9) ?A?R?S?A? I finally decided this was SACRISTAN but I'm still not too happy about the clue.
Thanks bibblebub and dave1948 - I bow to your superior brain power.
Yes dave1948, I won the CH a couple of years ago - a book, which I gave to my wife (the Catholic in the family) but I haven't sent any entries in lately.