Praise shown by Rex to Lord (5)
I believe the answer is:
extol
'praise' is the definition.
(I know that extol is a more specific form of the action praise)
'shown by rex to lord' is the wordplay.
'shown by' indicates the answer is hidden within the clue.
'EXTOL' can be found hidden inside 'rex to lord'.
(Other definitions for extol that I've seen before include "Talk up" , "Warmly approve of" , "Praise with enthusiasm" , "Praise enthusiastically" , "Highly rate" .)