Notice sailors on front of orlop deck (5)
I believe the answer is:
adorn
'deck' is the definition.
(I've seen this in another clue)
'notice sailors on front of orlop' is the wordplay.
'notice' becomes 'ad' (both can mean an advertisement).
'sailors' becomes 'RN' (abbreviation for Royal Navy).
'on' is a charade indicator (letters next to each other).
'front of' suggests taking the first letters (the letter at the front of the word).
The first letter of 'orlop' is 'o'.
'rn' after 'o' is 'orn'.
'ad'+'orn'='ADORN'
(Other definitions for adorn that I've seen before include "Make more attractive" , "get dressed!" , "Attire" , "Improve appearance" , "dress" .)