Maintain most of strength, getting hard to go on (4,5)
I believe the answer is:
hold forth
'go on' is the definition.
Both the answer and definition are verbs in their base form.
Perhaps they are linked in a way I don't understand?
'maintain most of strength getting hard' is the wordplay.
'maintain' becomes 'hold' (synonyms).
'most of' means to remove the last letter.
'strength' becomes 'forte' (synonyms).
'getting hard' becomes 'h' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'forte' with its final letter taken away is 'fort'.
'hold'+'fort'+'h'='HOLD FORTH'
'to' is the link.
Can you help me to learn more?
(Other definitions for hold forth that I've seen before include "Speak at length" , "lecture" , "make a speech" , "Offer" , "Speak lengthily, maybe preach" .)