Bad photographs show condition of early fliers (6)
I believe the answer is:
redeye
'of early fliers' is the definition.
The definition suggests a singular noun which matches the answer.
'bad photographs show condition' is the wordplay.
'bad photographs show' becomes 'red' (I am not sure about this - if you are sure you should believe this answer much more).
'condition' becomes 'eye condition' (eye condition is a kind of condition).
'red'+'eye'='REDEYE'
Can you help me to learn more?
(Other definitions for redeye that I've seen before include "Photographic problem" , "cheap whiskey" , "Fish; cheap whisky" , "Common fault in amateur flash photography" , "Poor whiskey - overnight flight" .)