A washer may need it and vice versa (3)
I believe the answer is:
tap
'a washer may need' is the definition.
I can't judge whether this defines the answer.
'it and vice versa' is the wordplay.
'it' becomes 't' (abbreviation. e.g. in 'tis).
'and' is a charade indicator (letters next to each other).
'vice versa' becomes 'ap' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
't'+'ap'='TAP'
Can you help me to learn more?
(Other definitions for tap that I've seen before include "that's less hard than 11 [BASH] or 22 [BATTER]" , "Water source; take advantage of" , "water supply" , "Light touch (hot or cold?)" , "Light blow; draw sap from (tree)" .)