Drone in centre of Heathrow -- odd (5)
I believe the answer is:
thrum
'drone' is the definition.
(I've seen this before)
'centre of heathrow odd' is the wordplay.
'centre of' says to take the centre.
'odd' becomes 'rum' (I've seen this before).
The centre of 'heathrow' is 'th'.
'th'+'rum'='THRUM'
'in' is the link.
(Other definitions for thrum that I've seen before include "Make a rhythmic hum" , "Make a continuous humming sound" , "Drum with fingers - bits of coarse yarn" , "bit of thread" , "Rhythmic buzzing sound - fringe left after weaving" .)