A post needing some acetylene welding (5)
I believe the answer is:
newel
'a post' is the definition.
(newel is a kind of post)
'some acetylene welding' is the wordplay.
'some' says the answer is hidden in the clue (some of the parts of the word are used).
'NEWEL' is hidden within 'acetylene welding'.
'needing' acts as a link.
(Other definitions for newel that I've seen before include "Post that's part of a flight of stairs" , "Post at the end of stairs" , "Yucatan native" , "Spiral stair central pillar" , "Post supporting stair rail" .)