收效 is a separable verb (离合词) meaning 'to produce results' or 'to take effect'. It's composed of 收 (to collect) and 效 (effect). As a verb-object phrase, you can split it by inserting 了, 过, or a measure word like 点 between the two syllables — for example, 收了效 ('has produced results') or 收了一点效 ('produced a little effect'). It is intransitive: you cannot say 收效 something directly; instead, use a topic-comment pattern (e.g. 这个办法收效很好) or a prepositional phrase (在...方面收效).