Medical containers maintaining temperature for organs (6)
I believe the answer is:
vitals
'organs' is the definition.
(I've seen this before)
'medical containers maintaining temperature' is the wordplay.
'medical containers' becomes 'vials' (I've seen this in another clue).
'maintaining' means one lot of letters goes inside another.
'temperature' becomes 't' (abbreviation).
'vials' placed around 't' is 'VITALS'.
'for' acts as a link.
(Other definitions for vitals that I've seen before include "Organs 21-ed for life" , "Organs essential for life" , "Essential organs of the body" , "The main organs of the body" , "Heart, lungs, brain etc" .)