Climbing, sex or bread? (4)
I believe the answer is:
roti
'bread?' is the definition.
(roti is a type of bread)
'climbing sex or' is the wordplay.
'climbing' says the letters should be written backwards (in a down clue, letters climb up).
'sex' becomes 'it' (common euphemism).
'it'+'or'='itor'
'itor' backwards is 'ROTI'.
(Other definitions for roti that I've seen before include "Indian flat round bread" , "Indian bread cooked on a griddle" , "Indian bread (not naan)" , "Indian flatbread" , "spicy sandwich" .)