Sailor’s tea urn oddly appearing (3)
I believe the answer is:
tar
'sailor's' is the definition.
(slang term for a sailor)
'tea urn oddly appearing' is the wordplay.
'oddly appearing' indicates alternate letters (letters in odd-numbered positions).
'tea'+'urn'='teaurn'
The alternate letters of 'teaurn' are 'TAR'.
(Other definitions for tar that I've seen before include "Black coat" , "Dark viscid substance" , "Black viscid substance" , "Sticky stuff for a kind of sailor" , "one may need to pay on boat" .)