Avoid Venetian magistrate incarcerating 500 (5)
I believe the answer is:
dodge
'avoid' is the definition.
(dodge can mean to avoid or evade)
'venetian magistrate incarcerating 500' is the wordplay.
'venetian magistrate' becomes 'doge' (historical term for the chief magistrate of Venice).
'incarcerating' is an insertion indicator (I've seen this in other clues).
'500' becomes 'D' (Roman numeral for 500).
'doge' placed around 'd' is 'DODGE'.
(Other definitions for dodge that I've seen before include "Get out of" , "Take evasive action" , "Move quickly to avoid" , "Avoid - Kansas city" , "Avoid - ruse" .)