Little protection for American reared transport animals (6)
I believe the answer is:
llamas
'transport animals' is the definition.
'little protection for american reared' is the wordplay.
'little' becomes 'small' ('small' can be a synonym of 'little').
'protection for' is an insertion indicator (some letters go around or protect others).
'american' becomes 'a' (common abbreviation - e.g. in organisation names).
'reared' is a reversal indicator (I've seen 'rearing' mean this (as in a horse rearing up)).
'small' enclosing 'a' is 'samall'.
'samall' reversed gives 'LLAMAS'.
(Other definitions for llamas that I've seen before include "South American pack animals" , "Andean pack animals" , "Sal and Mal for the animals" , "South American cud-chewing animals" , "Camel-like animals" .)