Condense mostly impressive book describing centre of Bratislava (9)
I believe the answer is:
epitomise
'condense' is the definition.
('condense'->'epitomize' is in my internal thesaurus and 'ize'->'ise')
'mostly impressive book describing centre of bratislava' is the wordplay.
'mostly' means to remove the last letter.
'impressive' becomes 'epic' (I've seen this before).
'book' becomes 'tome' (tome is a kind of book**).
'describing' indicates putting letters inside (describe can mean to form the outline of).
'centre of' says to take the centre.
The centre of 'bratislava' is 'is'.
'epic' with its last letter taken away is 'epi'.
'tome' placed around 'is' is 'tomise'.
'epi'+'tomise'='EPITOMISE'
(Other definitions for epitomise that I've seen before include "Abstract" , "Typify (S, not Z)" , "Act as representative" , "Embody perfectly a stated idea" , "Embody perfectly a stated quality" .)