Data coming back relating to an Ulster region (4)
I believe the answer is:
info
'data' is the definition.
(I've seen this before)
'coming back relating to an ulster region' is the wordplay.
'coming back' shows that the letters should be reversed in order.
'relating to' becomes 'of'.
'an ulster region' becomes 'NI' (Northern Ireland).
'of'+'ni'='ofni'
'ofni' in reverse letter order is 'INFO'.
(Other definitions for info that I've seen before include "Gen (colloq.)" , "Facts; knowledge gained" , "News" , "Knowledge (colloq.)" , "Latest" .)