Shakespearean character going by, catching start of one line (5)
I believe the answer is:
viola
'shakespearean character' is the definition.
(I've seen this before)
'going by catching start of one line' is the wordplay.
'going by' becomes 'via' (I am not sure about this - if you are sure you should believe this answer much more).
'catching' is an insertion indicator.
'start of' says to take the initial letters.
The first letters of 'one line' is 'ol'.
'via' placed around 'ol' is 'VIOLA'.
Can you help me to learn more?
(Other definitions for viola that I've seen before include "Shakespearean character" , "Shakespearean role" , "One played" , "Shakespeare heroine; instrument" , "big fiddle!" .)