Enter home quietly removing contents of unit (5)
I believe the answer is:
input
'enter' is the definition.
(I've seen this in another clue)
'home quietly removing contents of unit' is the wordplay.
'home' becomes 'in' (to be in is to be (at) home).
'quietly' becomes 'p' (p for piano and quiet).
'removing' becomes 'u' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'contents of' indicates the central letters (letters inside the word).
'unit' becomes 'katal' (SI unit of catalytic activity).
The centre of 'katal' is 't'.
'in'+'p'+'u'+'t'='INPUT'
Can you help me to learn more?
(Other definitions for input that I've seen before include "Data contributed" , "store" , "Person's contribution (to activity); electrical signal" , "Comment, contribution" , "Contribution; enter (data)" .)