Usual practice to have volunteers set up living area (7)
I believe the answer is:
habitat
'living area' is the definition.
(I've seen this before)
'usual practice to have volunteers set up' is the wordplay.
'usual practice' becomes 'habit' (I've seen this before).
'to have' is a charade indicator (letters next to each other).
'volunteers' becomes 'ta' (abbreviation for Territorial Army).
'set up' shows that the letters should be reversed in order.
'ta' reversed gives 'at'.
'habit'+'at'='HABITAT'
(Other definitions for habitat that I've seen before include "Living area" , "Environment in which an organism normally lives" , "Living environment" , "Territory" , "(Organism's) natural home" .)