Protective cover cold sailor put on end of oars (4)
I believe the answer is:
scab
'protective cover' is the definition.
'scab' can be an answer for 'cover' (I've seen this before). I'm not sure about the 'protective' bit.
'cold sailor put on end of oars' is the wordplay.
'cold' becomes 'C' (eg on taps).
'sailor' becomes 'ab' (abbreviation for able seaman).
'put on' means one lot of letters go next to another (some letters go on or after others).
'end of' says to take the final letters.
The final letter of 'oars' is 's'.
'c'+'ab'='cab'
'cab' put after 's' is 'SCAB'.
Can you help me to learn more?
(Other definitions for scab that I've seen before include "Dried crust on wound" , "Strikebreaker; mange" , "Rat" , "Sign of skin wound" , "Dried crust on sore" .)