Lawrence may return with promissory notes, being very determined (9)
I believe the answer is:
tenacious
'very determined' is the definition.
'tenacious' can be an answer for 'determined' (I've seen this before). I'm not sure about the 'very' bit.
'lawrence may return with promissory notes' is the wordplay.
'lawrence' becomes 'TE' (initials of TE Lawrence aka Lawrence of Arabia).
'may' becomes 'can' (synonyms).
'return' is a reversal indicator.
'with' means one lot of letters go next to another.
'promissory notes' becomes 'ious' (IOU is an example).
'can' back-to-front is 'nac'.
'te'+'nac'+'ious'='TENACIOUS'
'being' is the link.
Can you help me to learn more?
(Other definitions for tenacious that I've seen before include "Determined" , "Holding or sticking firmly" , "Dogged" , "refusing to give up" , "Persevering" .)