Warmer in Inverness unusually (3)
I believe the answer is:
sun
'warmer' is the definition.
(the sun warms things up)
'in inverness unusually' is the wordplay.
'in' indicates the answer is hidden within the clue.
'SUN' is hidden within 'inverness unusually'.
(Other definitions for sun that I've seen before include "Bask" , "Dawn riser" , "Centre of Earth's orbit" , "Rag" , "Centre of a solar system" .)