Gather that the boxer is slightly in the lead (5,2)
I believe the answer is:
round up
'gather' is the definition.
(I know that round up is a more specific form of the action gather)
'the boxer is slightly in the lead' is the wordplay.
I cannot quite understand how this works, but
'in the lead' could be 'up' (similar in meaning) and 'up' is located in the answer.
The remaining letters 'round' is a valid word which might be clued in a way I don't see.
This may be the basis of the clue (or it may be nonsense).
'that' acts as a link.
Can you help me to learn more?
(Other definitions for round up that I've seen before include "what mathematician may do to make approximation" , "rally" , "Summary" , "Group" , "Gather together" .)