Egyptians sang out with a sense of religious reverence (5)
I believe the answer is:
piety
'reverence' is the definition.
(piety is a kind of reverence)
'egyptians sang out with a sense of religious' is the wordplay.
I cannot really see how this works, but
'religious' could be 'pi' and 'pi' is found in the answer.
This may be the basis of clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for piety that I've seen before include "An unthinkingly accepted belief" , "Dutiful devotion" , "paying proper duty" , "Devotion to religious principles" , "Godly behaviour" .)