Constant temperature for competition (5)
I believe the answer is:
event
'competition' is the definition.
(I've seen this before)
'constant temperature' is the wordplay.
'constant' becomes 'even' (I've seen this before**).
'temperature' becomes 't' (abbreviation).
'even'+'t'='EVENT'
'for' is the link.
(Other definitions for event that I've seen before include "riding competition" , "What will happen" , "Significant happening" , "Happening, noteworthy perhaps" , "ride competitively" .)