Head of oil drilling company gives expression of surprise (3)
I believe the answer is:
coo
'expression of surprise' is the definition.
(I've seen this before)
'head of oil drilling company' is the wordplay.
'head of' suggests taking the first letters.
'drilling' means one lot of letters goes inside another (inserted letters drill through others).
'company' becomes 'co' (abbreviation).
The initial letter of 'oil' is 'o'.
'o' going within 'co' is 'COO'.
'gives' acts as a link.
(Other definitions for coo that I've seen before include "crumbs" , "Surprised expression" , "Murmur of a dove" , "Call like a dove" , "Sound made by dove" .)