Picked up grass with garden tool - I'm resigned to it! (5-2)
I believe the answer is:
heigh-ho
'i'm resigned to it' is the definition.
(phrase showing resignation or acceptance)
'picked up grass with garden tool' is the wordplay.
'picked up' shows a homophone (sound like).
'grass' becomes 'hay' (I have seen 'Mown grass ' mean 'hay' so perhaps 'grass' could also mean 'hay').
'with' says to put letters next to each other.
'garden tool' becomes 'ho' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'hay' sounds like 'heigh'.
'heigh'+'ho'='HEIGH-HO'
(Other definitions for heigh-ho that I've seen before include "Expression of resignation or boredom" , "Tired expression" , "Oh well, what can I do!" , "Expression of weariness" , "Gosh, I'm tired!" .)