How high trees grow in season around German city (10)

I believe the answer is:

timberline

'how high trees grow' is the definition.
(treeline on a mountain)

'season around german city' is the wordplay.
'season' becomes 'time' (both can mean a period).
'around' is an insertion indicator.
'german city' becomes 'berlin' (Berlin is the capital of Germany).
'time' enclosing 'berlin' is 'TIMBERLINE'.

'in' is the link.

I've seen this clue in The Times.

Want a hint initially instead of a full solution? Install my app