Welsh party MP daily excited about start of Cardiff rugby (5,5)
I believe the answer is:
plaid cymru
'welsh party' is the definition.
(Welsh political party)
'mp daily excited about start of cardiff rugby' is the wordplay.
I cannot quite understand how this works, but
'about' could be 'c' (abbreviation for circa) and 'c' is located in the answer.
an anagram of 'daily' is 'laidy' which is within the remaining letters.
'rugby' could be 'ru' and 'ru' is present in the answer.
This may be the basis of the clue (or it may be nonsense).
(Other definitions for plaid cymru that I've seen before include "party in Wales" , "party in UK" , "Welsh Nationalist party" , "Welsh political party" .)