Juliet's cousin turned up by a lake with dry clothing (6)
I believe the answer is:
tybalt
'juliet's cousin' is the definition.
(I've seen this in another clue)
'turned up by a lake with dry clothing' is the wordplay.
'turned up' says the letters should be written in reverse.
'lake' becomes 'L' (geographical abbreviation).
'with' says to put letters next to each other.
'dry' becomes 'tt' (abbreviation for teetotal).
'clothing' is an insertion indicator (some letters cover up or clothe others).
'by' in reverse letter order is 'yb'.
'yb'+'a'+'l'='ybal'
'ybal' put inside 'tt' is 'TYBALT'.
(Other definitions for tybalt that I've seen before include "Capulet's duelling kinsman" , "He hates, fights, Romeo" , "Killer of Mercutio (R&J)" , "killer of Montague" .)