Smallest lake towards where the sun rises (5)
I believe the answer is:
least
'smallest' is the definition.
(synonyms)
'lake towards where the sun rises' is the wordplay.
'lake' becomes 'L' (geographical abbreviation).
'towards' means one lot of letters go next to another (I've seen this in other clues).
'where the sun rises' becomes 'east' (I've seen this in another clue).
'l'+'east'='LEAST'
(Other definitions for least that I've seen before include "Lowest amount" , "Most insignificant" , "Minimal amount" , "Smallest (in significance)" , "Smallest, being stale" .)