Bubble over (7)
I believe the answer is:
enthuse
'bubble over' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for enthuse that I've seen before include "Excite - show excitement" , "Show lively interest and keenness" , "Wax lyrical (over)" , "Appear keenly interested" , "Express eager enjoyment, interest or approval" .)