Tough, one novel Sandy's penned? (6)
I believe the answer is:
sinewy
'tough' is the definition.
(similar in meaning)
'one novel sandy's penned?' is the wordplay.
I cannot quite understand how this works, but
'one' could be 'i' (Roman numeral) and 'i' is found in the answer.
'novel' could be 'new' (novel means new or fresh) and 'new' is located in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for sinewy that I've seen before include "Muscular" , "Muscly; fibrous" , "Tough, fibrous" , "strong" , "Toughly fibrous" .)