Do an absorbing job as cleaner (3,2)
I believe the answer is:
mop up
'do an' is the definition.
Although both the answer and definition are singular nouns, I can't understand how one could define the other.
'absorbing job as cleaner' is the wordplay.
'absorbing' is an insertion indicator.
'job as' becomes 'pu' (I can't justify this - if you can you should give a lot more credence to this answer).
'cleaner' becomes 'mop' (something which 'cleans').
'pu' inserted within 'mop' is 'MOP-UP'.
Can you help me to learn more?
(Other definitions for mop up that I've seen before include "Swab" , "Finish a task, clear away remnants" , "Kill (enemy stragglers)" , "take care of" , "Deal with spillage or defeated enemy" .)