Magistrates follow rest inside (5)
I believe the answer is:
doges
'magistrates' is the definition.
(doge is a kind of magistrate)
'follow rest inside' is the wordplay.
'follow' becomes 'dog' (I've seen this before).
'inside' indicates the central letters.
The middle letters of 'rest' are 'es'.
'dog'+'es'='DOGES'
(Other definitions for doges that I've seen before include "Chief magistrates of Venice and Genoa, formerly" , "Old Venetian magistrates" , "Former rulers of Venice" , "Former lords of Venice" .)