Praise in text oleaginously (5)
I believe the answer is:
extol
'praise' is the definition.
(extolling is a kind of praising)
'in text oleaginously' is the wordplay.
'in' indicates a hidden word.
'EXTOL' is hidden in the letters of 'text oleaginously'.
(Other definitions for extol that I've seen before include "be lavish with praise" , "Crack up" , "Lavishly praise" , "trumpet" , "Praise enthusiastically" .)