Deprived fellow in limp headgear (6)
I believe the answer is:
bereft
'deprived' is the definition.
(I've seen this before)
'fellow in limp headgear' is the wordplay.
'fellow' becomes 'f' (abbreviation - of a society etc.).
'in' means one lot of letters goes inside another.
'limp headgear' becomes 'beret' (beret is a kind of headgear. I am not sure about the 'limp' bit.).
'f' put within 'beret' is 'BEREFT'.
Can you help me to learn more?
(Other definitions for bereft that I've seen before include "Deprived of something precious" , "Deprived, of reason or loved one" , "Cut off - deprived" , "Sorrowful through loss" , "Having a deep sense of loss" .)