The smallest number left for the Orient (5)
I believe the answer is:
least
'the smallest' is the definition.
(I've seen this before)
'number left for the orient' is the wordplay.
'number left' becomes 'l' (common abbreviation. I am not sure about the 'number' bit.).
'for' means one lot of letters go next to another.
'the orient' becomes 'east' ('East' can be a synonym of 'orient').
'l'+'east'='LEAST'
Can you help me to learn more?
(Other definitions for least that I've seen before include "Bottom" , "Superlative form of 'little'" , "Lowest amount" , "No more petty" , "Opposite of most" .)