Street celebration on return from prison camp (6)
I believe the answer is:
stalag
'prison camp' is the definition.
(I've seen this before)
'street celebration on return' is the wordplay.
'street' becomes 'st' (abbreviation).
'celebration' becomes 'gala' (gala is a kind of celebration).
'on return' says the letters should be written in reverse.
'gala' back-to-front is 'alag'.
'st'+'alag'='STALAG'
'from' acts as a link.
(Other definitions for stalag that I've seen before include "WWII German prisoner of war camp" , "Type of German prison camp" , "German prison camp in WW2" , "German POW camp in WWII" , "German prisoner-of-war camp of WW2" .)