Indifferent to pressure in new diet (5)
I believe the answer is:
tepid
'indifferent' is the definition.
(I've seen this in another clue)
'pressure in new diet' is the wordplay.
'pressure' becomes 'p' (abbreviation).
'in' is an insertion indicator.
'new' is an anagram indicator.
'diet' is an anagram of 'teid'.
'p' inserted into 'teid' is 'TEPID'.
'to' is the link.
(Other definitions for tepid that I've seen before include "without passion" , "Luke warm" , "Slightly warm" , "Not very warm (water)" , "Of liquid, luke-warm" .)