Yoga accessory essential for amateur (3)
I believe the answer is:
mat
'yoga accessory' is the definition.
(I've seen this in another clue)
'essential for amateur' is the wordplay.
'essential for' says the answer is hidden in the clue (I've seen this in other clues).
'MAT' can be found hidden inside 'amateur'.
(Other definitions for mat that I've seen before include "Small rug" , "Unglossy floor pad" , "Foot-wiper on which welcome may be kept" , "What the cat sat on?" , "Floor-pad" .)