...complete with opening (5)
I believe the answer is:
whole
'complete' is the definition.
(associated in meaning)
'with opening' is the wordplay.
'with' becomes 'w' (abbreviation).
'opening' becomes 'hole' (hole is a kind of opening).
'w'+'hole'='WHOLE'
(Other definitions for whole that I've seen before include "Total" , "All the components" , "Integral" , "In entirety" , "Entire, undivided" .)