Group of engineers with ruddy huge screen (7)
I believe the answer is:
reredos
'screen' is the definition.
(a reredos is an ornamental screen)
'group of engineers with ruddy huge' is the wordplay.
'group of engineers' becomes 're' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'with' is a charade indicator (letters next to each other).
'ruddy' becomes 'red' (synonyms).
'huge' becomes 'os' (abbreviation for outsize).
're'+'red'+'os'='REREDOS'
Can you help me to learn more?
(Other definitions for reredos that I've seen before include "Wall decoration behind altar" , "Back of fireplace" , "Red rose could show a screen behind the altar" , "Church feature" , "Hanging in church" .)