Hold the last of the seamen in port (5)
I believe the answer is:
haven
'port' is the definition.
(I have seen 'Safe port ' mean 'haven' so perhaps 'port' could also mean 'haven')
'hold the last of the seamen' is the wordplay.
'hold' becomes 'have' ('have' can be a synonym of 'hold'**).
'the last of' indicates one should take the final letters.
The last letter of 'seamen' is 'n'.
'have'+'n'='HAVEN'
'in' acts as a link.
(Other definitions for haven that I've seen before include "Place of shelter" , "Small port, refuge" , "Sheltered port" , "Place of safety or sanctuary" , "Safe harbour" .)