Doing the thing in question out of gratitude? (2,2)
I believe the answer is:
at it
'doing the thing in question out' is the definition.
I don't know anything about this answer so I cannot judge whether it can be defined by this definition.
'of gratitude?' is the wordplay.
'of' indicates a hidden word.
'AT IT' is hidden within 'gratitude'.
Can you help me to learn more?
(Other definitions for at it that I've seen before include "occupied in a particular way" , "engaged in dubious activity?" , "working hard" , "Engaged in something particular" , "Busy" .)