Cool Dublin politician holds record, first in Ireland (5)
I believe the answer is:
tepid
'cool' is the definition.
(thesaurus)
'dublin politician holds record first in ireland' is the wordplay.
'dublin politician' becomes 'td' (Teachta Dala, term for an Irish parliamentarian).
'holds' indicates putting letters inside.
'record' becomes 'ep'.
'first in ireland' becomes 'i' (1st letter of 'ireland').
'ep'+'i'='epi'
'td' enclosing 'epi' is 'TEPID'.
(Other definitions for tepid that I've seen before include "Not very warm (water)" , "Unenthusiastic - cool" , "without passion" , "Showing little interest or enthusiasm" , "without enthusiasm" .)