Small domestic animal that is nursing temperature (6)
I believe the answer is:
petite
'small' is the definition.
(similar in meaning)
'domestic animal that is nursing temperature' is the wordplay.
'domestic animal' becomes 'pet' (I've seen this in another clue).
'that is' becomes 'ie' (short for Latin 'id est', 'that is').
'nursing' is an insertion indicator.
'temperature' becomes 't' (abbreviation).
'ie' going around 't' is 'ite'.
'pet'+'ite'='PETITE'
(Other definitions for petite that I've seen before include "Little French" , "Wee" , "Small, slim (girl)" , "Tie pet up, being small and dainty" , "Short" .)