Dainty foxtrot involved in line dancing (5)
I believe the answer is:
Here is my best explanation:
'dainty' is the definition.
'foxtrot involved in line dancing' is the subsidiary indication.
'foxtrot' becomes 'f' (phonetic alphabet: alpha, bravo, charlie etc.).
'involved in' is an insertion indicator.
'dancing' is an anagram indicator.
'line' anagrammed gives 'elin'.
'f' going inside 'elin' is 'elfin'.
(Other definitions for elfin that I've seen before include "Mischievous sprite", "Pixie-like", "Describing Santa's helpers", "Resembling one of the little people", "Fairy-like", "Small, delicate, mischievous and attractive", "Small, mischievous and charming", "Impish", "Sprite-like" and "Like a mischievous fairy".)