Former lieutenant welcoming ace's praise (5)
I believe the answer is:
exalt
'praise' is the definition.
(exalting is a kind of praising)
'former lieutenant welcoming ace's' is the wordplay.
'former' becomes 'ex'.
'lieutenant' becomes 'lt'.
'welcoming' is an insertion indicator (in sense of 'inviting in').
'ace' becomes 'a'.
'ex'+'lt'='exlt'
'exlt' enclosing 'a' is 'EXALT'.
(Other definitions for exalt that I've seen before include "Praise - latex (anag)" , "Laud" , "Aggrandize" , "Raise in rank, character, or status" , "Lift up in praise" .)