Lock-up legend with a bad temper (6)
I believe the answer is:
garage
'lock-up' is the definition.
'legend with a bad temper' is the wordplay.
'legend' becomes 'g' (leg-end - end letter of 'leg').
'with' says to put letters next to each other.
'bad temper' becomes 'rage'.
'g'+'a'+'rage'='GARAGE'
(Other definitions for garage that I've seen before include "Where car is housed" , "Car storage area" , "Car's home (or hospital?)" , "Building for housing automobiles" , "Domestic shelter for car" .)