Pipe is turned back; new plumbing at last stopping flood (6)
I believe the answer is:
engulf
'flood' is the definition.
(I've seen this before)
'pipe is turned back new plumbing at last stopping' is the wordplay.
'pipe' becomes 'flue' (flue pipe is a kind of pipe).
'is turned back' is a reversal indicator.
'new' becomes 'n' (common abbreviation eg NT for New Testament).
'at last' indicates one should take the final letters.
'stopping' indicates putting letters inside (inserted letters stop or plug a gap).
The final letter of 'plumbing' is 'g'.
'flue' backwards is 'eulf'.
'n'+'g'='ng'
'eulf' placed around 'ng' is 'ENGULF'.
(Other definitions for engulf that I've seen before include "Absorb or overwhelm" , "Swallow up, overwhelm" , "Swallow up like whirlpool" , "Deluge" , "Absorb, immerse" .)