Books tough rugby players (9)

I believe the answer is:

hardbacks

'books' is the definition.
(hardback is a kind of book)

'tough rugby players' is the wordplay.
'tough' becomes 'hard' (similar in meaning).
'rugby players' becomes 'backs' (back is a type of rugby player).
'hard'+'backs'='HARDBACKS'

I've seen this clue in The Guardian.

Want a hint initially instead of a full solution? Install my app