Latitude involved in rise of The Sun (5)
I believe the answer is:
solar
'of the sun' is the definition.
(solar means relating to the sun)
'latitude involved in rise' is the wordplay.
'latitude' becomes 'L' (abbreviation for latitude).
'involved in' is an insertion indicator.
'rise' becomes 'soar' (soar is a kind of rise).
'l' put within 'soar' is 'SOLAR'.
(Other definitions for solar that I've seen before include "type of radiation" , "Relating to our star" , "Sort of power" , "Sun-powered" , "Particular star's" .)