Tease tribe, endlessly (3)
I believe the answer is:
rib
'tease' is the definition.
(rib can mean to tease or mock)
'tribe endlessly' is the wordplay.
'endlessly' means to look at the middle letters (the ends of the words are removed).
The central letters of 'tribe' are 'RIB'.
(Other definitions for rib that I've seen before include "Large leaf-vein" , "Tease (sl.)" , "Tease; pectoral bone" , "structural member" , "Poke fun at the bone" .)