Talk effusively (4)
I believe the answer is:
gush
'talk effusively' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for gush that I've seen before include "Pour forth" , "Outburst" , "Sudden stream or jet" , "Pour out - appear overly effusive" , "Speak effusively" .)