A measure of fellowship (3)
I believe the answer is:
ell
'a measure' is the definition.
(historical unit of length)
'of fellowship' is the wordplay.
'of' indicates the answer is hidden within the clue.
'ELL' is hidden in the letters of 'fellowship'.
(Other definitions for ell that I've seen before include "Embellish with old measure of length" , "Old textile measure" , "Old 45-inch measure" , "Old cloth measure" , "Extension" .)