Fletcher's groove (4)
I believe the answer is:
etch
'groove' is the definition.
Although both the answer and definition are verbs in their base form, I can't see how one could define the other.
'fletcher's' is the wordplay.
'ETCH' is hidden within the letters.
However, I am unsure how the hidden word is indicated.
Can you help me to learn more?
(Other definitions for etch that I've seen before include "What most engravers presumably find easy to do" , "Imprint vividly" , "Carve (design) on a surface" , "Cut into a block used for printing" , "Design by eating out" .)