Slender point on missile (6)
I believe the answer is:
narrow
'slender' is the definition.
(similar in meaning)
'point on missile' is the wordplay.
'point' becomes 'N' (N is an example).
'on' is a charade indicator (letters next to each other).
'missile' becomes 'arrow' (arrow is a kind of missile).
'n'+'arrow'='NARROW'
(Other definitions for narrow that I've seen before include "Closely confining" , "Having little breadth" , "Fine" , "Circumscribed" , "Restrict" .)