Popular hotel on river within a company (2-5)
I believe the answer is:
in-house
'within a company' is the definition.
(I've seen this before)
'popular hotel on river' is the subsidiary indication.
'popular' becomes 'in'.
'hotel' becomes 'h' (phonetic alphabet: alpha, bravo, charlie etc.).
'on' is a charade indicator (letters next to each other).
'river' becomes 'ouse' (**).
'in'+'h'+'ouse'='inhouse'
(Other definitions for in-house that I've seen before include "Within the organisation" , "Within a company" .)