Link with temperature that is popular (3-2)
I believe the answer is:
tie-in
'link with' is the definition.
(thesaurus)
'temperature that is popular' is the wordplay.
'temperature' becomes 't' (abbreviation).
'that is' becomes 'ie' (short for Latin 'id est', 'that is').
'popular' becomes 'in' ('in' can mean trendy).
't'+'ie'+'in'='TIE-IN'
(Other definitions for tie-in that I've seen before include "Book, etc, linked to film, TV show" , "Something linked to another item or event" , "Relationship" , "Association, connection" , "Related item" .)