Column to endure when given external support (8)
I believe the answer is:
pilaster
'column' is the definition.
(pilaster is a kind of column)
'endure when given external support' is the wordplay.
'endure' becomes 'last' (synonyms).
'when given external' means one lot of letters goes inside another (some letters go outside or external to others).
'support' becomes 'pier' (pier is a kind of support).
'last' inserted inside 'pier' is 'PILASTER'.
'to' is the link.
(Other definitions for pilaster that I've seen before include "Decorative column standing out from the fa?ade of a building" , "Rectangular column projected from wall" , "Rectangular column support projecting slightly from a wall" , "Piles tar into a form of column" , "Square column" .)