Counterfeit pens left in bar (5)
I believe the answer is:
flake
'bar' is the definition.
(I know that Flake is a bar)
'counterfeit pens left' is the wordplay.
'counterfeit' becomes 'fake' (synonyms).
'pens' is an insertion indicator (inserted letters are held or penned in).
'left' becomes 'l' (common abbreviation).
'fake' enclosing 'l' is 'FLAKE'.
'in' is the link.
(Other definitions for flake that I've seen before include "Small chipping" , "Flat thin fragment" , "Sliver" , "Piece of falling snow" , "Chipped piece of stone" .)