Direction given by leading ecologists at seminar talks (4)
I believe the answer is:
east
'direction' is the definition.
(compass direction)
'leading ecologists at seminar talks' is the wordplay.
'leading' suggests taking the first letters (the leading letter of the word).
The first letters of 'ecologists at seminar talks' is 'EAST'.
'given by' acts as a link.
(Other definitions for east that I've seen before include "Direction of the Orient" , "Tom's schoolfellow" , "Bridge player" , "Sunrise direction" , "Ninety degree bearing" .)