Cut around the base of horn and grind (5)
I believe the answer is:
gnash
'grind' is the definition.
(gnashing is a kind of grinding)
'cut around the base of horn' is the wordplay.
'cut' becomes 'gash' ('gash' can be a synonym of 'cut'**).
'around' is an insertion indicator.
'the base of' suggests the final letters.
The final letter of 'horn' is 'n'.
'gash' placed around 'n' is 'GNASH'.
'and' acts as a link.
(Other definitions for gnash that I've seen before include "grate" , "Grind one's teeth" , "Grind (teeth) together" , "Grind away" , "grinding action" .)