Hard to enter false figure (11)
I believe the answer is:
tetrahedron
'figure' is the definition.
(I've seen this before)
'hard to enter false' is the wordplay.
'false' indicates anagramming the letters.
'hard'+'to'+'enter'='hardtoenter'
'hardtoenter' is an anagram of 'TETRAHEDRON'.
(Other definitions for tetrahedron that I've seen before include "Body with four triangular faces" , "Four-sided solid" , "Four-faced solid" , "Pyramid" , "Four-sided figure" .)