Tackling Romulan Empire Kirk starts journey (4)
I believe the answer is:
trek
'journey' is the definition.
(I know that trek is a type of journey)
'tackling romulan empire kirk starts' is the wordplay.
'starts' indicates taking the first letters.
The initial letters of 'tackling romulan empire kirk' is 'TREK'.
(Other definitions for trek that I've seen before include "Long hard journey on foot" , "Long walk in the mountains?" , "A long arduous journey as in S Africa" , "Long walk, expedition" , "Long hike" .)