Hmmm, indeed! The J is certainly right because it answers this clue:
Sluggish, wasting time aboard pleasure craft (7).
I've got JOINERY, which is certainly correct.
Here's another clue I haven't been able to figure out even though I have an answer:
Minister runs and exercises in spotless clothing (9).
These are the letters I had:
C - - - G - M - N
My answer is CLERGYMAN
It's a minister. But I couldn't make sense of the rest of the clue.
Finished now and I don't care! But this crossword has made me feel as if my poor brain has deserted me.