I live with cross mountain climber? (4)
I believe the answer is:
ibex
'mountain climber?' is the definition.
(I've seen this in another clue)
'i live with cross' is the wordplay.
'live' becomes 'be' (synonyms).
'with' means one lot of letters go next to another.
'cross' becomes 'x' (X is cross-shaped).
'i'+'be'+'x'='IBEX'
(Other definitions for ibex that I've seen before include "Mountain goat with long curved horns" , "being nimble-footed" , "one seldom puts a foot wrong" , "Mountain-goat" , "Wild goat with large recurved horns" .)