Ten photos developed there and then
I believe the answer is:
on the spot
'there and then' is the definition.
(I've seen this before)
'ten photos developed' is the wordplay.
'developed' indicates anagramming the letters.
'ten'+'photos'='tenphotos'
'tenphotos' with letters rearranged gives 'ON-THE-SPOT'.
(Other definitions for on the spot that I've seen before include "Challenged" , "Where face cream may be applied" , "Where cream may go" , "In a difficult situation?" , "replacing ball from pocket here?" .)