Reserve acquired by old company head (7)
I believe the answer is:
iciness
'reserve' is the definition.
(I've seen this in another clue)
'old company head' is the wordplay.
'old company' becomes 'ici' (former company Imperial Chemical Industries).
'head' becomes 'ness' (ness is a headland).
'ici'+'ness'='ICINESS'
'acquired by' is the link.
(Other definitions for iciness that I've seen before include "Extreme cold" , "Hostile attitude" , "Frozen state of" , "Hostile or cold nature" , "Chill; reserve" .)