Outgrowth (4)
'outgrowth' is the definition.
(I know that horn is a type of outgrowth)
This is all the clue.
(Other definitions for horn that I've seen before include "Brass musical instrument" , "Instrument - rhino's appendage" , "familiar to the matador?" , "Hollow outgrowth and musical instrument" , "Musical instrument; Chile Cape" .)
'outgrowth' is the definition.
(I know that outgrowth can be written as offshoot)
This is all the clue.
(Other definitions for offshoot that I've seen before include "Branch, derivative" , "new branch" , "Shoo toff away with something subsidiary" , "Small branch growing from the main stem" , "Branch attached to the main stem" .)