Reading for one’s partner no longer suitable for him or her (6)
I believe the answer is:
unisex
'suitable for him or her' is the definition.
The definition suggests a singular noun but the answer is not.
'reading for one's partner no longer' is the wordplay.
'reading for one's' becomes 'unis' (I can't explain this - if you can you should believe this answer much more).
'partner no longer' becomes 'ex' (I've seen this in other clues).
'unis'+'ex'='UNISEX'
Can you help me to learn more?
(Other definitions for unisex that I've seen before include "Gender-inclusive" , "Available to men and women, clothes or hairdressing salons" , "Suitable for male and female" , "Of clothing, hairstyles etc - suitable for men and women" , "for boys and girls" .)