Busy finding an opening in fuel distribution (8)
I believe the answer is:
eventful
'busy' is the definition.
(similar in meaning)
'an opening in fuel distribution' is the wordplay.
'an opening' becomes 'vent' (vent is a kind of opening).
'in' means one lot of letters goes inside another.
'distribution' is an anagram indicator.
'fuel' is an anagram of 'eful'.
'vent' going into 'eful' is 'EVENTFUL'.
'finding' acts as a link.
(Other definitions for eventful that I've seen before include "Full of incident, not dull" , "Notable, full of incidents" , "Lively and exciting" , "Busy, exciting (period)" , "Packed with action, lots happening" .)