Swim with hot skimpy garment: Kate has one! (9)
I believe the answer is:
diphthong
'kate has one' is the definition.
I can't tell whether this defines the answer.
'swim with hot skimpy garment' is the wordplay.
'swim' becomes 'dip' (dip is a kind of swim).
'with' says to put letters next to each other.
'hot' becomes 'h'.
'skimpy garment' becomes 'thong' (I've seen this before).
'dip'+'h'+'thong'='DIPHTHONG'
Can you help me to learn more?
(Other definitions for diphthong that I've seen before include "Sound combining two vowels" , "the thing in middle of cruise" , "Combination of two vowels" , "Sound of two vowels in one syllable" , "Ligature of vowels" .)