Part of lighthouse is large — money put up by Royal Navy (7)
I believe the answer is:
lantern
'part of lighthouse' is the definition.
'lantern' can be an answer for 'lighthouse' (thesaurus). I'm not sure about the 'part of' bit.
'large money put up by royal navy' is the wordplay.
'large money' becomes 'l' (L can mean 'pounds'. I am not sure about the 'large' bit.).
'put up' becomes 'ante' (I've seen this in another clue).
'by' says to put letters next to each other.
'royal navy' becomes 'RN' (abbreviation for Royal Navy).
'l'+'ante'+'rn'='LANTERN'
'is' is the link.
Can you help me to learn more?
(Other definitions for lantern that I've seen before include "Transparent case for holding a light" , "Enclosed light" , "Encased light" , "Light in a transparent protective case" , "Light in a protective casing" .)