Once a year found waters around peninsula unnavigable when travelling back (6)
I believe the answer is:
annual
'once a year' is the definition.
(I've seen this before)
'waters around peninsula unnavigable when travelling back' is the wordplay.
'ANNUAL' is hidden backwards in amongst the letters.
But, I am not sure how this is indicated.
'found' is the link.
Can you help me to learn more?
(Other definitions for annual that I've seen before include "Coming once a year" , "Occurring once every year" , "Type of year book" , "Plant that lives and dies within one year" , "Occuring once a year" .)