This is almost some fibre (5)
I believe the answer is:
sisal
'fibre' is the definition.
(sisal is a kind of fibre)
'this is almost some' is the wordplay.
'some' indicates a hidden word.
'SISAL' is hidden within 'this is almost'.
(Other definitions for sisal that I've seen before include "Agave yielding fibre" , "Rope fibre from leaves of tropical plant" , "constituent of rope" , "material for painter, say?" , "Fibrous plant used for rope" .)