Eaglet ultimately has solitary short claw (5)
I believe the answer is:
talon
'claw' is the definition.
(I know that talon is a type of claw)
'eaglet ultimately has solitary short' is the wordplay.
'ultimately' suggests the final letters.
'has' says to put letters next to each other.
'solitary' becomes 'alone' (synonyms).
'short' means to remove the last letter.
The final letter of 'eaglet' is 't'.
'alone' with its final letter taken away is 'alon'.
't'+'alon'='TALON'
(Other definitions for talon that I've seen before include "Bird of prey's claw" , "hunting hook" , "Large claw" , "Claw of a bird of prey" , "part to make savage cuts" .)