Make certain before the sun breaks through (6)
I believe the answer is:
ensure
'make certain' is the definition.
(synonyms)
'before the sun breaks through' is the wordplay.
I cannot really see how this works, but
'before' could be 'e' (I've seen this in other clues) and 'e' is found in the answer.
an anagram of 'sun' is 'nsu' which is present in the answer.
The remaining letters 're' is a valid word which might be clued in a way I don't understand.
This may be the basis of clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for ensure that I've seen before include "Make certain, confirm" , "warrant" , "See run (anag)" , "Guarantee" , "Make certain, secure" .)