Fibrous, sinewy (7)
I believe the answer is:
stringy
I believe this is a double definition.
'fibrous' is the first definition.
(I know that fibrous can be written as stringy)
'sinewy' is the second definition.
(I know that sinewy can be written as stringy)
(Other definitions for stringy that I've seen before include "(Of food) tough, fibrous" , "Tall, wiry, thin" , "Old runners can be so" .)