Going around a lake, my waterproof covering (6)
I believe the answer is:
galosh
'waterproof covering' is the definition.
(waterproof shoe)
'going around a lake my' is the wordplay.
'going around' means one lot of letters goes inside another.
'lake' becomes 'L' (geographical abbreviation).
'my' becomes 'gosh' (both are expressions of surprise).
'a'+'l'='al'
'al' going into 'gosh' is 'GALOSH'.
(Other definitions for galosh that I've seen before include "Waterproof shoe" , "Waterproof overshoe" , "singular footwear" , "Rubber overshoe" , "Wellington" .)