Car leaving Nicaragua crushed lizard (6)
I believe the answer is:
iguana
'lizard' is the definition.
(iguana is a kind of lizard)
'car leaving nicaragua crushed' is the wordplay.
'leaving' indicates named letters should be taken away.
'crushed' is an anagram indicator.
'nicaragua' with 'car' taken out is 'niagua'.
'niagua' with letters rearranged gives 'IGUANA'.
(Other definitions for iguana that I've seen before include "Tropical American lizard" , "Animal" , "Type of lizard" , "Creature" , "Large tree-climbing specimen of 5 down in tropical America" .)