The master isn’t reading the book thoroughly (7)
I believe the answer is:
skipper
'the master' is the definition.
(synonyms)
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for skipper that I've seen before include "Trawler boss" , "sleep in outhouse" , "girl with rope?" , "one that's put over the side" , "Chap aboard trawler" .)