Mine volunteers some bread (5)
I believe the answer is:
pitta
'some bread' is the definition.
(pitta is a type of bread)
'mine volunteers' is the wordplay.
'mine' becomes 'pit' (down the pit).
'volunteers' becomes 'TA' (abbreviation for Territorial Army).
'pit'+'ta'='PITTA'
(Other definitions for pitta that I've seen before include "Greek unleavened bread" , "Middle Eastern bread" , "Type of flat bread that's split to hold a filling" , "Partially-leavened bread of the Near East" , "Type of flatbread" .)