Sorry absconder firstly imaginative hiding record (10)
I believe the answer is:
apologetic
'sorry' is the definition.
(saying sorry)
'absconder firstly imaginative hiding record' is the wordplay.
'firstly' says to take the initial letters.
'imaginative' becomes 'poetic' (I've seen this before).
'hiding' is an insertion indicator.
'record' becomes 'log' (log is a kind of record).
The initial letter of 'absconder' is 'a'.
'poetic' placed around 'log' is 'pologetic'.
'a'+'pologetic'='APOLOGETIC'
(Other definitions for apologetic that I've seen before include "Acknowledging faults" , "Regretful" , "Acknowledging failure" , "Expressing regret" , "Contrite" .)