Heats up, after slip welcomes end of Phil Salt (8)

'salt' is the definition.
(sulphate is a kind of salt)

'heats up after slip welcomes end of phil' is the wordplay.
'after' means one lot of letters go next to another.
'slip' indicates anagramming the letters.
'welcomes' is an insertion indicator (in sense of 'invites in').
'end of' indicates one should take the final letters.
The last letter of 'phil' is 'l'.
'heats'+'up'='heatsup'
'heatsup' with letters rearranged gives 'suphate'.
'suphate' going around 'l' is 'SULPHATE'.