Jack could go to it in house arrest (3)
I believe the answer is:
sea
'jack could go to it' is the definition.
I can't judge whether this definition defines the answer.
'in house arrest' is the wordplay.
'in' indicates a hidden word.
'SEA' is hidden in the letters of 'house arrest'.
Can you help me to learn more?
(Other definitions for sea that I've seen before include "The Med, e.g." , "Ocean area" , "E.g Aral or Weddell" , "Vast expanse" , "that's easily reached from Dover?" .)