Drench girl dancing around with relatives (13)
I believe the answer is:
grandchildren
'relatives' is the definition.
(grandchild is a kind of relative)
'drench girl dancing around with' is the wordplay.
'dancing' indicates anagramming the letters.
'around' means one lot of letters goes inside another.
'with' becomes 'and'.
'drench'+'girl'='drenchgirl'
'drenchgirl' is an anagram of 'grchildren'.
'grchildren' placed around 'and' is 'GRANDCHILDREN'.
(Other definitions for grandchildren that I've seen before include "Offspring of one's offspring" , "relatives" , "Junior members of family" .)