Angel hurries up to catch Paternoster’s opening (6)
I believe the answer is:
Here is my best explanation:
'angel' is the definition.
(seraph is a kind of angel)
'hurries up to catch paternoster's opening' is the subsidiary indication.
'hurries' becomes 'hares' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'up' says the letters should be written backwards (in down clue: letters go upwards).
'to catch' is an insertion indicator.
'opening' says to take the initial letters.
The first letter of 'paternoster' is 'p'.
'hares' back-to-front is 'serah'.
'serah' going around 'p' is 'seraph'.
(Other definitions for seraph that I've seen before include "Heavenly creature", "angel of the highest order", "Phrase distorted for the heavenly being", "Angelic character", "Phase for angel", "Turn of phase for an angel", "Angel - phrase (anag)", "Angel with winged head of child", "Phrase (anag.)" and "It's heavenly".)