Caught by publicity about group (5)
I believe the answer is:
cadre
'group' is the definition.
(cadre is a kind of group)
'caught by publicity about' is the wordplay.
'caught' becomes 'c' (cricket abbreviation).
'by' means one lot of letters go next to another.
'publicity' becomes 'ad' (advert).
'about' becomes 're' (regarding**).
'c'+'ad'+'re'='CADRE'
(Other definitions for cadre that I've seen before include "Small (military) unit capable of expansion when necessary" , "Raced around with basic military unit" , "Tight-knit military unit" , "Raced around with army unit" , "activist group" .)