Single family member shortly joined terror cell (4)
I believe the answer is:
isis
'terror cell' is the definition.
Although both the answer and definition are singular nouns, I cannot understand how one could define the other.
'single family member shortly joined' is the wordplay.
'single' becomes 'i' (one).
'family member shortly' becomes 'sis' (short for sister; 'shortly' suggests a short form).
'joined' is a charade indicator (letters next to each other).
'i'+'sis'='ISIS'
Can you help me to learn more?
(Other definitions for isis that I've seen before include "Oxford's second eight" , "Oxford river; goddess" , "academic stream?" , "Divine female" , "Egyptian goddess - Thames at Oxford" .)