Rents complex from Government with most of the power (8)
I believe the answer is:
Here is my best explanation:
'power' is the definition.
(strength is a kind of power)
'rents complex from government with most of the' is the subsidiary indication.
'complex' is an anagram indicator.
'from' indicates anagramming the letters (from the letters).
'government' becomes 'g'.
'with' is a charade indicator (letters next to each other).
'most of' means to remove the last letter.
'the' with its last letter removed is 'th'.
'rents' with letters rearranged gives 'stren'.
'g' after 'th' is 'thg'.
'thg' with letters rearranged gives 'gth'.
(Other definitions for strength that I've seen before include "Toughness, force", "Potency - firmness", "Power", "Vigour, potency", "Good attribute", "stamina", "Physical potency", "vigour", "The longest one-syllable word in English - might" and "Concentration".)