Company on ship is extremely efficient and will protect them (6)
I believe the answer is:
cosset
'will protect them' is the definition.
I can't tell whether this definition defines the answer.
'company on ship is extremely efficient' is the wordplay.
'company' becomes 'co' (abbreviation).
'on' means one lot of letters go next to another (in a down clue, letters appear on others).
'ship' becomes 'SS' (prefix in ship names eg SS Great Britain).
'is extremely' suggests removing the centre (only the extremes of the word are used).
'efficient' with its middle taken out is 'et'.
'co'+'ss'+'et'='COSSET'
'and' is the link.
Can you help me to learn more?
(Other definitions for cosset that I've seen before include "Treat indulgently, pamper" , "Care for overindulgently" , "Fondle" , "Treat with excessive indulgence" , "Pamper and spoil" .)