Boasts of loads welcoming Republican (5)
I believe the answer is:
brags
'boasts' is the definition.
(brag is a kind of boast)
'loads welcoming republican' is the wordplay.
'loads' becomes 'bags' (both can mean large amounts).
'welcoming' means one lot of letters goes inside another (in sense of 'inviting in').
'republican' becomes 'r' (abbreviation).
'bags' placed around 'r' is 'BRAGS'.
'of' acts as a link.
(Other definitions for brags that I've seen before include "Crows" , "Boasts" .)