At war camp, little child that grows up (10)
I believe the answer is:
stalagmite
'that grows up' is the definition.
'at war camp little child' is the wordplay.
'at' is a charade indicator (letters next to each other).
'war camp' becomes 'stalag' (German prisoner of war camp).
'little child' becomes 'mite'.
'stalag' next to 'mite' is 'STALAGMITE'.
(Other definitions for stalagmite that I've seen before include "One growing up in a cave" , "One that grows up" , "found on floor of cave" , "What may form on cave floor" , "Pillar of the underground" .)