Lag (8)
'lag' is the definition.
(I know that trail is a more specific form of the action lag)
This is the entire clue.
(Other definitions for trail that I've seen before include "Rural footpath" , "Mark left where something has passed - follow it" , "Drag; path" , "Track made through wild country" , "Track or scent used in following someone" .)
(Other definitions for prisoner that I've seen before include "Gaol inmate" , "Person doing porridge?" , "Person held captive as by law" , "Person behind bars" , "One is incarcerated" .)
'lag' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for insulate that I've seen before include "Lean suit (anag.)" , "Protect from heat, cold, noise etc" , "Thermally protect" , "Cover or protect with a utensil (8)" , "Protect (from, eg, heat)" .)