Entertainment penning lines linked to low aspect of heavenly body (4,4)
I believe the answer is:
full moon
'aspect of heavenly body' is the definition.
Although both the answer and definition are singular nouns, I cannot see how one could define the other.
'entertainment penning lines linked to low' is the wordplay.
'entertainment' becomes 'fun' (fun is something entertaining).
'penning' is an insertion indicator.
'lines' becomes 'll' (two abbreviations for line).
'linked to' is a charade indicator (letters next to each other).
'low' becomes 'moo' (both can mean to make a cow noise).
'll'+'moo'='llmoo'
'fun' enclosing 'llmoo' is 'FULL MOON'.
Can you help me to learn more?
(Other definitions for full moon that I've seen before include "Lunar display with full disc illuminated" , "monthly highlight?" , "Bright time of the month" , "Wholly illuminated satellite" .)