Clue: Like e.g. Cameron once welcoming southern European national, / perhaps warn one going after bit of ice creamier than the rest? (8, 8)
Answer: IVORIEST/ESTONIAN
Explanation: Definition: creamier than the rest
I[ce] + VOR (a word from King Lear that perhaps means "warn") I (one). This is the "somewhat fanciful" superlative mentioned in the preamble / S in ETONIAN (David Cameron is famously an old Etonian)