Book Hearts defender needing a way in (8)
I believe the answer is:
hardback
'book' is the definition.
(I know that hardback is a type of book)
'hearts defender needing a way in' is the wordplay.
'hearts' becomes 'h' (abbreviation used in card games e.g. bridge).
'defender' becomes 'back' (left-backs and right-backs are football defenders).
'needing' is a charade indicator (letters next to each other).
'way' becomes 'rd' (short for road).
'in' means one lot of letters goes inside another.
'back' put after 'a' is 'aback'.
'aback' placed around 'rd' is 'ardback'.
'h'+'ardback'='HARDBACK'
(Other definitions for hardback that I've seen before include "Sort of book" , "It might be a novel!" , "Penguins are rarely so" , "Style of book binding" , "Durable version of book" .)