Terribly rash glance reveals heavenly spirits (10)
I believe the answer is:
archangels
'heavenly spirits' is the definition.
'archangels' can be an answer for 'spirits' (I have seen 'high spirits' mean 'archangels' so perhaps 'spirits' could also mean 'archangels'). I am unsure of the 'heavenly' bit.
'terribly rash glance' is the wordplay.
'terribly' indicates an anagram.
'rash'+'glance'='rashglance'
'rashglance' with letters rearranged gives 'ARCHANGELS'.
'reveals' acts as a link.
Can you help me to learn more?
(Another definition for archangels that I've seen is " high spirits".)