Come to a point (5)
'come to a point' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for taper that I've seen before include "Become narrow" , "One making recording" , "Gradually come to a point" , "Wind down" , "Narrow towards the end" .)
(Other definitions for narrow that I've seen before include "contract" , "Small-minded" , "Small in breadth" , "Restricted in width." , "... not one" .)