Group of workers reportedly steal clothing item (5)
I believe the answer is:
tunic
'clothing item' is the definition.
(tunic was a historical type of clothing)
'group of workers reportedly steal' is the wordplay.
'group of workers' becomes 'tu' (Trade Union).
'reportedly' indicates a 'sounds like' (homophone) clue.
'steal' becomes 'nick' (nick can informally mean to steal).
'nick' sounds like 'nic'.
'tu'+'nic'='TUNIC'
(Other definitions for tunic that I've seen before include "School garment" , "Schoolgirl's dress" , "Dress for soldier" , "Loose fitting light cloak extending to the hip or lower" , "Roman garment" .)