A letter from Berlin , perhaps, may be relevant (7)
I believe the answer is:
germane
'relevant' is the definition.
(germane can mean relevant or pertinent)
'a letter from berlin perhaps' is the wordplay.
I cannot really understand how this works, but
'a' could be 'an' and 'an' is present in the answer.
'letter' could be 'r' and 'r' is found in the answer.
This may be the basis of the clue (or it may be nonsense).
'may be' acts as a link.
Can you help me to learn more?
(Other definitions for germane that I've seen before include "Relevant to current topic" , "Material" , "Relevant, to the point" , "Relevant (to subject)" , "Relative or appropriate" .)