### Clue: Heading west, note around river pale Arctic animal (7)
### Answer: NARWHAL 
 ### Explanation: Definition: Arctic animal
 **Reversal of**(Heading west, in an across clue) { LAH(alternative for "la", syllable representing the 6th note in a musical scale) + [R(abbrev. for "river") **contained in**(around …) WAN(pale, say, from sickness)] } .
To fit the answer, the second part of the wordplay should be read as "round river, pale" – a little Yoda-speak.