One of four children in short panic in special vehicle (5,3)
I believe the answer is:
squad car
'special vehicle' is the definition.
(police vehicle)
'one of four children in short panic' is the wordplay.
'one of four children' becomes 'quad' (short for quadruplet).
'in' is an insertion indicator.
'short' means to remove the last letter.
'panic' becomes 'scare' (synonyms).
'scare' with its final letter removed is 'scar'.
'quad' placed into 'scar' is 'SQUAD CAR'.
'in' acts as a link.
(Other definitions for squad car that I've seen before include "panda perhaps" , "Police patrol vehicle" , "Force vehicle" , "Police wheels?" , "vehicle from station" .)