University invested in Lamb’s complete essays? Praise be! (8)
I believe the answer is:
'praise be' is the definition.
'university invested in lamb's complete essays?' is the wordplay.
I cannot really see how this works, but
'university' could be 'u' and 'u' is found in the answer.
'complete' could be 'all' ('all' can be similar in meaning to 'complete') and 'all' is present in the answer.
'lamb' could be 'elia' (pseudonym of essayist Charles Lamb) and 'elia' is located in the remaining letters.
No letters remain.
This may be the basis of clue (or it may be nonsense).
(Other definitions for alleluia that I've seen before include "Interjection meaning praise to God, from Hebrew" , "Biblical exhortation of praise to the Lord" , "God be praised" , "Hebrew word meaning praise to God" , "Religious word to express praise or thanks" .)