Old sailors had to be decorated (6)
I believe the answer is:
ornate
'be decorated' is the definition.
(similar in meaning)
'old sailors had' is the wordplay.
'old' becomes 'o' (common abbreviation eg in OE for Old English).
'sailors' becomes 'RN' (abbreviation for Royal Navy).
'had' becomes 'ate' (e.g. I had an ice cream).
'o'+'rn'+'ate'='ORNATE'
'to' acts as a link.
(Other definitions for ornate that I've seen before include "Elaborately decorated, perhaps overdone" , "Highly embellished" , "Richly or elaborately decorated" , "Over-decorated" , "Baroque" .)