Means to enter with surgery to save Kelvin's rib (4,4)
I believe the answer is:
pork chop
'rib' is the definition.
(a pork chop may be cut from a rib)
'means to enter with surgery to save kelvin's' is the wordplay.
'means to enter' becomes 'porch' (porch is a type of entrance).
'with' is a charade indicator (letters next to each other).
'surgery' becomes 'op' (short for operation).
'to save' is an insertion indicator.
'kelvin' becomes 'K' (abbreviation for the unit of temperature).
'porch'+'op'='porchop'
'porchop' enclosing 'k' is 'PORK-CHOP'.
(Other definitions for pork chop that I've seen before include "Pigmeat on the bone" , "Slice from a pig's rib" .)