I think the first part is:
Of 17 Meadow Cottages
The Friary (?)
Salisbury
and (? or 2nd ?)
Wife of ----
Scammell
a ----
I would guess from this that her husband's surname was Scammell but neither his forename nor his occupation were given. The informant, probably a hospital employee, may simply not have known.
The cause of death section is:
(1) Chronic Bright's
Disease. Duration
not known
(2) Chronic Dilation
of stomach. Duration
not known
Suppurative Cholecystitis
(from gallstones)
Tuberculosis
of left Pleura PM Certified by
Sydney J Cole (?)
"PM" probably indicates that a postmortem was carried out. From the GRO's guide (PDF) to death certificates, "Certified" means " the cause of death was given by the doctor in medical attendance of the deceased", i.e. Sydney Cole.
I think that the "primary" cause of death is (1), and (2) was causative or contributory to (1). The following non-numbered entries are other significant health issues that may have contributed to the death but were not immediate causes.
The final note is indeed a correction, and it appears itself to have been corrected, judging by the struck out text:
Clerical error
in Col 6
Corrected on
the 8th February
1918
on the authority
of the Registrar
General
By me
Arthur Mitchell
Registrar
in the presence
of
O Sheppard (?)
Supt Registrar
Column 6 is the cause of death. If you look at the bottom of that section, "pleura" is written in above a crossed-out word that I can't read clearly. I think that is the correction of the clerical error that this refers to.