In case it changes, so absorbed and keen (12)
I believe the answer is:
enthusiastic
'keen' is the definition.
(I've seen this before)
'in case it changes so absorbed and' is the wordplay.
I cannot really see how this works, but
'it' could be 't' (abbreviation. e.g. in 'tis) and 't' is found within the answer.
'so' could be 'as' (e.g. phrases like 'not as tall' and 'not so tall') and 'as' is found within the answer.
'and' could be 'n' (common abbreviation for 'and') and 'n' is present in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for enthusiastic that I've seen before include "Full of fervour" , "Ardent - thin suitcase (anag)" , "Showing great interest" , "Gung-ho" , "warm" .)