Sailor's hat boy and I found in lake (9)
I believe the answer is:
tarpaulin
'sailor's' is the definition.
(thesaurus)
'hat boy and i found in lake' is the wordplay.
'hat boy' becomes 'paul' (I can't justify this - if you can you should believe this answer much more).
'and' means one lot of letters go next to another.
'found in' means one lot of letters goes inside another.
'lake' becomes 'tarn' (tarn is a kind of lake).
'paul'+'i'='pauli'
'pauli' put into 'tarn' is 'TARPAULIN'.
Can you help me to learn more?
(Other definitions for tarpaulin that I've seen before include "Waterproof cloth" , "oilskin hat" , "protective cover" , "Waterproofed canvas" , "Heavy waterproof canvas" .)