Place with extremes of temperature, the Spanish Main (7)
I believe the answer is:
chelsea
'place' is the definition.
(I have seen 'place of buns' mean 'chelsea' so perhaps 'place' could also mean 'chelsea')
'with extremes of temperature the spanish main' is the wordplay.
'with' is a charade indicator (letters next to each other).
'extremes of temperature' becomes 'C H' (abbreviations for cold and hot).
'the spanish' becomes 'el' ('the' in Spanish).
'main' becomes 'sea' (the main is an old name for the sea).
'ch'+'el' is 'chel'.
'chel'+'sea'='CHELSEA'
(Other definitions for chelsea that I've seen before include "Part of Manhattan" , "Cheyne Walk neighbourhood?" , "Word linking boot and bun" , "The Blues of Stamford Bridge" , "Bun, pensioner or flower-show" .)