Metal mass Luigi Pirandello holds up (3)
I believe the answer is:
pig
'metal mass' is the definition.
Although both the answer and definition are singular nouns, I don't see how one could define the other.
'luigi pirandello holds up' is the wordplay.
'holds' indicates the answer is hidden within the clue.
'up' says the letters should be written backwards (in down clue: letters go upwards).
'gip' can be found hidden inside 'luigi pirandello'.
'gip' reversed gives 'PIG'.
Can you help me to learn more?
(Other definitions for pig that I've seen before include "& 16 Animal pen" , "Eat ravenously" , "One scoffs" , "Greedy eater" , "Hog" .)