Would take essence of arrowroot desultorily in retirement (4,2)
I believe the answer is:
used to
'would take essence' is the definition.
'used to' can be an answer for 'would' (eg 'I used to dance then' is 'I would dance then'). I am unsure of the 'take essence' bit.
'of arrowroot desultorily in retirement' is the wordplay.
'of' indicates a hidden word.
'in retirement' says the letters should be written backwards (retire can mean to go back or backwards).
'otdesu' can be found hidden inside 'arrowroot desultorily'.
'otdesu' in reverse letter order is 'USED TO'.
Can you help me to learn more?
(Other definitions for used to that I've seen before include "Not unfamiliar with" , "Was in the habit" , "Familiar with" , "Accustomed or inured" , "Did at times in the past" .)