Nothing standard in old POW camp (5)
I believe the answer is:
oflag
'old pow camp' is the definition.
(type of German prisoner of war camp in WW1 and WW2)
'nothing standard' is the wordplay.
'nothing' becomes 'O' (O resembles 0).
'standard' becomes 'flag' (I've seen this in another clue).
'o'+'flag'='OFLAG'
'in' acts as a link.
(Other definitions for oflag that I've seen before include "Place of internment" , "German prisoner-of-war camp for officers" , "now-disused camp" , "Place for detention" , "Colditz, for example" .)