Plant yielding fibre that’s primarily fine and soft (4)
I believe the answer is:
flax
'plant yielding fibre' is the definition.
Although both the answer and definition are singular nouns, I can't understand how they can define each other.
'primarily fine and soft' is the wordplay.
'primarily' indicates taking the first letters.
'and' means one lot of letters go next to another.
'soft' becomes 'lax' (synonyms).
The initial letter of 'fine' is 'f'.
'f'+'lax'='FLAX'
'that's' acts as a link.
Can you help me to learn more?
(Other definitions for flax that I've seen before include "Blue flowering plant cultivated for its seeds and fibre" , "Fibre from a plant with blue flowers, used to make linen" , "Fibre woven to make linen" , "Source of linseed" , "Plant cropped for linen" .)