Course given in arms (8)
I believe the answer is:
bearings
'arms' is the definition.
(thesaurus)
'course given in' is the wordplay.
'course' becomes 'bearing' (I've seen this before).
'given in' becomes 's' (I can't justify this - if you can you should believe this answer much more).
'bearing'+'s'='BEARINGS'
Can you help me to learn more?
(Other definitions for bearings that I've seen before include "Compass directions or small balls in wheel hubs" , "Moving parts; directions" , "(One's) orientation" , "Ivan -, Russian author" , "(Sense of) one's position or direction" .)