Girl has cracked bumper somewhat (7)
I believe the answer is:
largish
'bumper somewhat' is the definition.
I can't judge whether this definition defines the answer.
'girl has cracked' is the wordplay.
'cracked' indicates anagramming the letters.
'girl'+'has'='girlhas'
'girlhas' is an anagram of 'LARGISH'.
Can you help me to learn more?
(Other definitions for largish that I've seen before include "Somewhat hefty" , "sizeable proportions" , "Fairly big" , "Comfortable shoe" , "Of considerable extent" .)