One's temperature raised with inflammation and fatigue (9)
I believe the answer is:
tiredness
'fatigue' is the definition.
('tiredness' can be a synonym of 'fatigue')
'one's temperature raised with inflammation' is the wordplay.
'one' becomes 'i' (Roman numeral).
'temperature' becomes 't' (abbreviation).
'raised' shows that the letters should be reversed in order.
'with' says to put letters next to each other.
'inflammation' becomes 'redness' ('redness' can be a synonym of 'inflammation'**).
'i'+'t'='it'
'it' reversed gives 'ti'.
'ti'+'redness'='TIREDNESS'
'and' is the link.
(Other definitions for tiredness that I've seen before include "Weary feeling" , "Lassitude; residents (anag.)" , "Weariness" , "Exhaustion" , "That's liable to occur at midnight" .)