Arguably, only half are used skilfully (4)
![Ross](/clue/static/ross-mug.min.png)
I believe the answer is:
ably
'skilfully' is the definition.
'arguably only half are' is the wordplay.
'ABLY' is hidden within the letters.
But, I am not sure how the hidden word is indicated.
'used' is the link.
Can you help me to learn more?
(Other definitions for ably that I've seen before include "In proficient manner" , "With competence" , "Competently" , "Masterfully" , "With great skill" .)