3 vehicle clamped in Kensington Gardens (5)
I believe the answer is:
tonga
'3 vehicle clamped' is the definition.
I can't judge whether this definition defines the answer.
'in kensington gardens' is the wordplay.
'in' indicates a hidden word.
'TONGA' is hidden in the letters of 'kensington gardens'.
(Other definitions for tonga that I've seen before include "Pacific island state" , "S.W Pacific Kingdom" , "Tropic island" , "Do a bad tango in the Pacific archipelago" , "group of Pacific islands" .)