Forwards alien parcel (6)
I believe the answer is:
packet
'parcel' is the definition.
(packet is a kind of parcel)
'forwards alien' is the wordplay.
'forwards' becomes 'pack' (Rugby term).
'alien' becomes 'et' (extra terrestrial).
'pack'+'et'='PACKET'
(Other definitions for packet that I've seen before include "bomb" , "Data transmission unit - large sum" , "Old boat" , "A boat; large sum of money" , "Sachet" .)