Giving great yawns, tedious chore ends (8)
I believe the answer is:
Here is my best explanation:
'giving' is the definition.
'great yawns tedious chore ends' is the subsidiary indication.
'great' becomes 'large' ('large' can be a synonym of 'great'**).
'ends' suggests the final letters.
The last letters of 'yawns tedious chore' are 'sse'.
(Other definitions for largesse that I've seen before include "charity", "Bounty, gift", "Generous giving", "Magnanimous bestowal of gifts", "Munificence", "Generosity in giving gifts", "Generous disposal of gifts", "Generosity in gift-giving", "Eelgrass (anag.)" and "Magnanimity, munificence".)