Grovelling sailor caught boarding fast plane (6)
I believe the answer is:
abject
'grovelling' is the definition.
(I've seen this before)
'sailor caught boarding fast plane' is the wordplay.
'sailor' becomes 'ab' (abbreviation for able seaman).
'caught' becomes 'c' (cricket abbreviation).
'boarding' is an insertion indicator.
'fast plane' becomes 'jet' (I've seen this in another clue).
'c' placed into 'jet' is 'ject'.
'ab'+'ject'='ABJECT'
(Other definitions for abject that I've seen before include "Lacking all dignity" , "Wretched, worthless" , "feeble" , "Down-hearted" , "Low in spirit or hope" .)