Bread given in trench much appreciated (5)
I believe the answer is:
pitta
'bread' is the definition.
(pitta is a type of bread)
'trench much appreciated' is the wordplay.
'trench' becomes 'pit' (trench is a type of pit).
'much appreciated' becomes 'ta' (both are ways of saying thank you).
'pit'+'ta'='PITTA'
'given in' is the link.
(Other definitions for pitta that I've seen before include "Greek unleavened bread" , "Flat sort of bread" , "Flat hollow unleavened bread" , "Middle Eastern bread" , "Type of flat bread that's split to hold a filling" .)