Trouble returning with Republican fabulist (4)
I believe the answer is:
liar
'fabulist' is the definition.
(I've seen this in another clue)
'trouble returning with republican' is the wordplay.
'trouble' becomes 'ail' (synonyms).
'returning' shows that the letters should be reversed in order.
'with' is a charade indicator (letters next to each other).
'republican' becomes 'R' (abbreviation).
'ail' written backwards gives 'lia'.
'lia'+'r'='LIAR'
(Other definitions for liar that I've seen before include "Dissembler" , "Fabricator" , "Story teller?" , "not straight [one]" , "One whose pants are on fire?" .)