Climber supports promoting people in toilet (5)
I believe the answer is:
privy
'toilet' is the definition.
(I know that privy is a type of toilet)
'climber supports promoting people' is the wordplay.
'climber' becomes 'ivy' (ivy is a climbing plant).
'supports' says to put letters next to each other (bottom letters provide a support for the top ones).
'promoting people' becomes 'pr' (I can't justify this - if you can you should give a lot more credence to this answer).
'ivy' put after 'pr' is 'PRIVY'.
'in' acts as a link.
Can you help me to learn more?
(Other definitions for privy that I've seen before include "John" , "sort of councillor" , "Aware of" , "Participating in the knowledge of something secret" , "Party to secret knowledge - outside loo" .)