In report, betray group of spies (4)
I believe the answer is:
cell
'group of spies' is the definition.
'cell' can be an answer for 'group' (thesaurus). I am not sure about the 'of spies' bit.
'in report betray' is the wordplay.
'in report' indicates a 'sounds like' (homophone) clue (ie reportedly, \'we hear\').
'betray' becomes 'sell' (synonyms).
'sell' is a homophone of 'CELL'.
Can you help me to learn more?
(Other definitions for cell that I've seen before include "Basic biological unit" , "Basic unit of living matter" , "required for current generation?" , "Small room for nun, monk or prisoner" , "Unit of animal or plant structure" .)