One is glad to be so close (9)
I believe the answer is:
alongside
'close' is the definition.
(I've seen this before)
'one is glad to be' is the wordplay.
'to be' indicates an anagram.
'one'+'is'+'glad'='oneisglad'
'oneisglad' anagrammed gives 'ALONGSIDE'.
'so' is the link.
(Other definitions for alongside that I've seen before include "Bordering" , "Aligned so as to be next to, as ship moored to pier" , "Parallel to" , "Adjacent to" , "Age-old sin (anag.)" .)