He's good to give a seaman half a bottle (5)
I believe the answer is:
abbot
'he's good' is the definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
'give a seaman half a bottle' is the wordplay.
'give' says to put letters next to each other.
'a seaman' becomes 'ab' (short for able seaman).
'half a' suggests halving the letters.
'bottle' with half the letters taken is 'bot'.
'ab'+'bot' is 'ABBOT'.
'to' acts as a link.
Can you help me to learn more?
(Other definitions for abbot that I've seen before include "Monastic authority" , "Convent leader, male" , "chap who'll be over order?" , "Brother" , "Head of monastery" .)