Compilers welcoming liberal pioneers (8)
I believe the answer is:
settlers
'pioneers' is the definition.
'compilers welcoming liberal' is the wordplay.
'compilers' becomes 'setters' (compilers or setters of cryptic crosswords).
'welcoming' means one lot of letters goes inside another (in sense of 'inviting in').
'liberal' becomes 'l' (abbreviation).
'setters' going around 'l' is 'SETTLERS'.
(Other definitions for settlers that I've seen before include "Immigrants" , "Trestles for pioneers" , "Pioneers, homesteaders" , "Colonists" , "who pay their bills?" .)