Prove to be true provided there's light outside (6)
I believe the answer is:
verify
'prove to be true' is the definition.
(I've seen this in another clue)
'provided there's light outside' is the wordplay.
'provided there' becomes 'if' (eg 'provided it's sunny' means 'if it's sunny'. I am not sure about the 'there' bit.).
'light' becomes 'very' (I've seen this before).
'outside' is an insertion indicator.
'if' put within 'very' is 'VERIFY'.
Can you help me to learn more?
(Other definitions for verify that I've seen before include "Prove to be true" , "Confirm the truth of" , "Demonstrate" , "Check to be true" , "Support" .)