Decided to buy and to give up gallivanting (6,4)
I believe the answer is:
settle down
'give up gallivanting' is the definition.
I can't judge whether this defines the answer.
'decided to buy and' is the wordplay.
'decided' becomes 'settled' ('settle' can be a synonym of 'decide').
'to buy' becomes 'ow' (I can't justify this - if you can you should give a lot more credence to this answer).
'and' becomes 'n' (common abbreviation for 'and').
'settled'+'ow'+'n'='SETTLE DOWN'
'to' acts as a link.
Can you help me to learn more?
(Other definitions for settle down that I've seen before include "put down roots" , "Become quiet and orderly" .)