Look before you take such a year (4)
I believe the answer is:
leap
'year' is the definition.
(leap year is a kind of year)
'look before you take such a' is the wordplay.
I cannot quite understand how this works, but
'a' is found in the answer.
The remaining letters 'lep' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for leap that I've seen before include "'Look before you . . . .'" , "Jump; type of year" , "Pounce" , "Jump a long way" , "Jump across" .)