Adaptable piece of art nail pinned up (6)
I believe the answer is:
pliant
'adaptable' is the definition.
(I've seen this before)
'of art nail pinned up' is the wordplay.
'of' indicates a hidden word.
'up' shows that the letters should be reversed in order (in down clue: letters go upwards).
'tnailp' is hidden within 'art nail pinned'.
'tnailp' in reverse letter order is 'PLIANT'.
'piece' is the link.
(Other definitions for pliant that I've seen before include "Able to move supply" , "Flexible and easily manipulated" , "Adaptable" , "Bending easily" , "Flexible - yielding" .)