Run through support and choose sides (6)
I believe the answer is:
pierce
'run through' is the definition.
(I've seen this before)
'support and choose sides' is the wordplay.
'support' becomes 'pier' (pier is a kind of support).
'and' means one lot of letters go next to another.
'sides' means to remove the middle letters (only the letters on the sides are used).
'choose' with its centre taken out is 'ce'.
'pier'+'ce'='PIERCE'
(Other definitions for pierce that I've seen before include "Make hole in for recipe" , "Stab" , "Make hole in with something sharp" , "Stick a pin in" , "Cut a way through" .)