Myself and Beatle lost good sheep (6)
I believe the answer is:
merino
'sheep' is the definition.
(breed of sheep)
'myself and beatle lost good' is the wordplay.
'myself' becomes 'me'.
'and' says to put letters next to each other.
'beatle' becomes 'ringo' (Ringo Starr).
'lost' suggests deleting specific letters.
'good' becomes 'g' (abbreviation).
'ringo' with 'g' taken away is 'rino'.
'me'+'rino'='MERINO'
(Other definitions for merino that I've seen before include "Can this sheep be found in Rome?" , "Fine soft woolen yarn" , "Fine-woolled sheep" , "No rime for this sheep" , "Fine woollen yarn" .)