Statement of conditionality is accepted by province (4)
I believe the answer is:
nisi
'statement of conditionality is accepted by province' is the definition.
I can't tell whether this definition defines the answer.
'is accepted by province' is the wordplay.
'accepted by' means one lot of letters goes inside another.
'province' becomes 'ni' (I've seen this in other clues).
'is' going inside 'ni' is 'NISI'.
Can you help me to learn more?
(Other definitions for nisi that I've seen before include "Kind of divorce decree" , "Unless - in Latin" , "'De mortuis nil .... bonum.'" , "(Of decree) taking effect when conditions are met" , "(Of decree) valid if certain conditions are met" .)