Praise is no longer key (5)
I believe the answer is:
exalt
'praise' is the definition.
(I know that exalt is a type of praise)
'no longer key' is the wordplay.
'no longer' becomes 'ex' (prefix meaning former or onetime).
'key' becomes 'alt' (the Alt keyboard button).
'ex'+'alt'='EXALT'
'is' acts as a link.
(Other definitions for exalt that I've seen before include "Raise high, glorify" , "Honour - raise up" , "Extol" , "Laud" , "delight" .)