Piece of information I came across on the way back (4)
I believe the answer is:
item
'piece of information' is the definition.
(I've seen this before)
'i came across on the way back' is the wordplay.
'came across' becomes 'met' ('meet' can be a synonym of 'come across').
'on the way back' is a reversal indicator.
'met' in reverse letter order is 'tem'.
'i'+'tem'='ITEM'
(Other definitions for item that I've seen before include "Matter" , "Element" , "two with a link" , "Record" , "story" .)