Cambrian (5)
I believe the answer is:
'cambrian' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for welsh that I've seen before include "Owain Glyndwr?" , "From Aberystwyth, for instancewelshw" , "Nationality of Dai or Ivor" , "From Swansea, say?" , "tongue" .)