US state was riveting, I gathered (4,8)
I believe the answer is:
west virginia
'us state' is the definition.
(I've seen this before)
'was riveting i gathered' is the wordplay.
'gathered' is an anagram indicator.
'was'+'riveting'+'i'='wasrivetingi'
'wasrivetingi' is an anagram of 'WEST VIRGINIA'.
(Other definitions for west virginia that I've seen before include "State of eastern US" , "Eastern American state" , "US state, capital Charleston" , "US state, forming part of 5 until 1863" .)