Feeble politician supporting endless fabrication (4)
I believe the answer is:
limp
'feeble' is the definition.
(I've seen this before)
'politician supporting endless fabrication' is the wordplay.
'politician' becomes 'MP' (Member of Parliament).
'supporting' means one lot of letters go next to another (in a down clue, some letters go below others).
'endless' means to remove the last letter.
'fabrication' becomes 'lie' (a lie is an invention or fabrication).
'lie' with its last letter taken off is 'li'.
'mp' put after 'li' is 'LIMP'.
(Other definitions for limp that I've seen before include "exhausted" , "Weak" , "Slack, wilted" , "Drag a leg" , "Floppy" .)