Show lively interest (7)
I believe the answer is:
enthuse
'show lively interest' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for enthuse that I've seen before include "Tunes he adapted to feel eager liking for" , "Show strong approval" , "Seem keen" , "Show eagerness" , "Show feeling of eager liking and approval" .)