Moving Sara's things, keen person who's deceitful (5,2,3,5)
I believe the answer is:
snake in the grass
'person who's deceitful' is the definition.
I can't judge whether this definition defines the answer.
'moving sara's things keen' is the wordplay.
'moving' indicates anagramming the letters (letters are moved around).
'saras'+'things'+'keen'='sarasthingskeen'
'sarasthingskeen' is an anagram of 'SNAKE IN THE GRASS'.
Can you help me to learn more?
(Other definitions for snake in the grass that I've seen before include "Treacherous person" , "one shouldn't meet with one on the Emerald Isle?" , "unsuspected danger" , "Hidden danger" , "Judas?" .)