Former chief magistrate imprisoning duke for deception (5)
I believe the answer is:
dodge
'for deception' is the definition.
(I've seen this in another clue)
'former chief magistrate imprisoning duke' is the wordplay.
'former chief magistrate' becomes 'doge' (as in the Doges of Venice).
'imprisoning' indicates putting letters inside.
'duke' becomes 'd' (abbreviation).
'doge' placed around 'd' is 'DODGE'.
(Other definitions for dodge that I've seen before include "A quick evasive movement" , "Avoid; cunning trick" , "Western city" , "Ploy" , "Evade by moving out of the way" .)