One's complete attention devoted to sucking up (10)
I believe the answer is:
absorption
'sucking up' is the definition.
(I've seen this before)
'one's complete attention devoted to' is the wordplay.
I cannot quite understand how this works, but
'one' could be 'i' (Roman numeral) and 'i' is present in the answer.
'to' is present in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for absorption that I've seen before include "sucking up" , "Assimilating" , "(Process of) taking in" , "Process of soaking up" .)