Intruder - rest managed to go by with hesitation (10)
I believe the answer is:
trespasser
'intruder' is the definition.
(I know that intruder can be written as trespasser)
'rest managed to go by with hesitation' is the wordplay.
'managed' is an anagram indicator.
'to go by' becomes 'pass' ('pass' can be a synonym of 'go by').
'with' says to put letters next to each other.
'hesitation' becomes 'er' (sound used when hesitating).
'rest' is an anagram of 'tres'.
'tres'+'pass'+'er'='TRESPASSER'
(Other definitions for trespasser that I've seen before include "Intruder into another's land" , "Illegal enterer of land" , "Misplaced individual" , "One unlawfully entering another's land" , "sinner" .)