One in caravan approached lake (5)
I believe the answer is:
camel
'one in caravan' is the definition.
(I've seen this before)
'approached lake' is the wordplay.
'approached' becomes 'came' (come can mean to approach or get closer).
'lake' becomes 'L' (geographical abbreviation).
'came'+'l'='CAMEL'
(Other definitions for camel that I've seen before include "It is called the ship of the desert" , "A ship, some say" , "fawn" , "Humped ungulate" , "Dromedary, perhaps" .)