Wanting to see girl in capital of Germany (7)
I believe the answer is:
missing
'wanting' is the definition.
(wanting can mean lacking or missing)
'girl in capital of germany' is the wordplay.
'girl' becomes 'miss' (term of address for an unmarried woman).
'capital of' indicates taking the first letters.
The initial letter of 'germany' is 'g'.
'miss'+'in'+'g'='MISSING'
'to see' is the link.
(Other definitions for missing that I've seen before include "Absent with location unknown" , "Not to be found" , "Lost without" .)