Sexy type mostly teases one helping wash up (7)
I believe the answer is:
dishrag
'one helping wash up' is the definition.
(cloth for washing up)
'sexy type mostly teases' is the wordplay.
'sexy type' becomes 'dish' (dish can mean an attractive person).
'mostly' means to remove the last letter.
'teases' becomes 'rags' ('rag' can be a synonym of 'tease').
'rags' with its final letter removed is 'rag'.
'dish'+'rag'='DISHRAG'
(Other definitions for dishrag that I've seen before include "American tea towel" , "used to clean in kitchen" , "Cleaner" , "Wiper in the kitchen" , "Washing-up cloth" .)