Message about large fibres (4)
I believe the answer is:
flax
'message about large fibres' is the definition.
I can't tell whether this definition defines the answer.
'message about large' is the wordplay.
'message' becomes 'fax' ().
'about' indicates putting letters inside.
'large' becomes 'L' (eg in clothes sizes).
'fax' placed around 'l' is 'FLAX'.
Can you help me to learn more?
(Other definitions for flax that I've seen before include "Fibre from a plant with blue flowers, used to make linen" , "Blue flowering plant cultivated for its seeds and fibre" , "Source of linen" , "Textile fibre from a blue-flowered plant" , "leaves from it make cloth" .)