Through which to see a girl's love for Romeo (5)
I believe the answer is:
visor
'through which to' is the definition.
I can't tell whether this defines the answer.
'a girl's love for romeo' is the wordplay.
'a girl's' becomes 'Vis' (short for Violet).
'love' becomes 'o' (love means zero in tennis).
'for' means one lot of letters go next to another.
'romeo' becomes 'r' (phonetic alphabet: alpha, bravo, charlie etc.).
'vis'+'o'+'r'='VISOR'
'see' is the link.
Can you help me to learn more?
(Other definitions for visor that I've seen before include "Eyeshade" , "Eye protector" , "piece of armour" , "Sunshade" , "Part of an armour helmet" .)