Trick magistrate to lock up Democrat (5)
I believe the answer is:
dodge
'trick' is the definition.
(I've seen this before)
'magistrate to lock up democrat' is the wordplay.
'magistrate' becomes 'doge' (doge is a kind of magistrate).
'to lock up' indicates putting letters inside.
'democrat' becomes 'd'.
'doge' placed around 'd' is 'DODGE'.
(Other definitions for dodge that I've seen before include "Avoid by sudden movement" , "Ploy" , "Avoid - Kansas city" , "Evade - trick" , "Evade by moving out of the way" .)