There may be other apps like this as well, but I use “Akebi” on my Android phone, and it has a really nice feature for looking up words where you know one kanji but not the other(s).
You can search with ‘?’ and then fill in the missing Kanji either by typing or drawing them, and then see the result of all words that fit that pattern.
For example, if you see the word 納得 and you know the right-hand kanji is “得る (to earn)”, you can:
- Enter “??” and search
- Press on the second “?” and enter “える” in the search box and select 得 from the dropdown
- Press the double ^ symbol to replace the second ‘?’ with your choice – search will now show results for “?得” (i.e. all two-character words where the second character is 得)
- If the word you are looking for still isn’t showing, you can press the other ‘?’ and try drawing it out.
Jisho.org also supports a similar-style wildcard search (e.x. search for “?得”), but I find the app on my phone easier if I’m in the middle of a game. Also, if you have to draw out the character, drawing is a lot easier with my finger on the phone screen than a mouse on the computer.